Chapter II: Part 2

The western portion of the Sahara is apparently not so hot as the eastern portion. The mean annual temperature for Biskra is 20.3° C.; for Ghardaia it is 21° C.; for El Golea it is 22.2° C.; and for Touggourt it is 23.4° C. The mean temperature at Cairo is 21.3° C.; for Suez it is 21.5° C.; and for Djedda, on the Red Sea, it is 27.3° C. The absolute maximum temperatures in southern Algeria for as many years and for two of the most southern army posts, El Golea and In Salah, are as follows: El Golea, 47°, 46.5°, 48°, and 49.2° C.; In Salah, 50.0°, 49.2°, 50.2°, and 48° C.; at Ouargla the maxima are 50.2°, 51°, 52°, 49°, and 48.4° C. On account of the fact that in the western Sahara at these stations in winter there are usually freezing temperatures, the yearly range of temperature is 50.0° C., or over. The greatest range reported for the western Sahara is that for Ghardaia as given by Engler, namely, 57°, from -7° to 50° C. At Timmimoun, 1904, the range was from -3.0° to 53.1° C., or one of 56.1° C. The extreme absolute daily range in temperature on the desert appears not to exceed that of certain stations on the High Plateau, although, as shown below, the temperature variations on the desert may be much larger than the records indicate. At Laghouat and at Ghardaia the thermometers which I exposed showed a daily range of from 10.5° to 12.5° C. only. The instruments were placed on the outside of buildings, and usually on the second story. As a contrast to this observed diurnal variation, an opportunity was given to take temperatures on the open desert at a time when the days were fairly warm and the nights were rather cold. The place was between Touggourt and Ouargla. At 3 o’clock on the afternoon of November 26, 1910, the shade temperature at the place in question was 23° C. During the night the thermometer registered -1.7° C. as the minimum, thus showing a drop of 24.7° C. in something over 12 hours. Table 9 gives the extreme daily range in temperature for three years observed at the stations named.

TABLE 9.—_Absolute daily range in temperature._

+----------+-------+-------+-------+-------+-------+-------+
| Station. | Jan. | Feb. | Mar. | Apr. | May. | June. |
+----------+-------+-------+-------+-------+-------+-------+
| | _°C._ | _°C._ | _°C._ | _°C._ | _°C._ | _°C._ |
| In Salah | 21.6 | 23.0 | 24.4 | 24.6 | 22.0 | 23.2 |
| Ouargla | 20.8 | 25.4 | 24.0 | 25.0 | 27.0 | 26.0 |
+----------+-------+-------+-------+-------+-------+-------+
[**Continued]

+----------+-------+-------+-------+-------+-------+-------+
| Station. | July. | Aug. | Sept. | Oct. | Nov. | Dec. |
+----------+-------+-------+-------+-------+-------+-------+
| | _°C._ | _°C._ | _°C._ | _°C._ | _°C._ | _°C._ |
| In Salah | 23.4 | 22.0 | 29.0 | 20.0 | 23.4 | 22.6 |
| Ouargla | 26.0 | 27.8 | 24.6 | 23.0 | 20.0 | 23.8 |
+----------+-------+-------+-------+-------+-------+-------+

A further examination of the maximum temperatures shows certain climatic features of interest and of great importance as factors in the environment of the desert plants, especially the high average maxima and the large amount of heat received in the desert, as indicated by a summation of the maximal temperatures. That the greatest daily temperatures must be high is indicated by table 10, which gives the average maxima for three to five years at three typical desert stations.

TABLE 10.—_Average maximum temperatures._

+----------+-------+-------+-------+-------+-------+-------+
| Station. | Jan. | Feb. | Mar. | Apr. | May. | June. |
+----------+-------+-------+-------+-------+-------+-------+
| | _°C._ | _°C._ | _°C._ | _°C._ | _°C._ | _°C._ |
| Ouargla | 21.9 | 18.3 | 30.9 | 37.8 | 41.1 | 47.1 |
| El Golea | 23.0 | 25.8 | 35.6 | 27.5 | 40.9 | 44.4 |
| In Salah | 27.4 | 30.1 | 37.2 | 41.0 | 43.4 | 47.6 |
+----------+-------+-------+-------+-------+-------+-------+
[**Continued]

+----------+-------+-------+-------+-------+-------+-------+
| Station. | July. | Aug. | Sept. | Oct. | Nov. | Dec. |
+----------+-------+-------+-------+-------+-------+-------+
| | _°C._ | _°C._ | _°C._ | _°C._ | _°C._ | _°C._ |
| Ouargla | 49.4 | 47.7 | 44.3 | 40.0 | 31.0 | 25.0 |
| El Golea | 47.5 | 46.0 | 43.8 | 36.7 | 29.9 | 22.4 |
| In Salah | 44.3 | 47.1 | 45.9 | 41.3 | 37.0 | 27.1 |
+----------+-------+-------+-------+-------+-------+-------+

The maximum temperatures show that the total amount of heat received on the desert, as compared to that received in the climatic provinces nearer the sea, is not only great, but also that the amount is variable on the desert itself, one station receiving much more heat at certain times of the year than another station. The total heat for each station is arrived at by adding up the daily maxima for the midseasonal months, January, April, July, and October, and dividing by the number of years whose records were consulted. The amounts given in table 11 are the averages for three to four years, for three desert stations and for one station in the Tell.

TABLE 11.—_Sums of the daily maximum temperatures._

+--------------+----------+--------+-------+----------+
| Station. | January. | April. | July. | October. |
+--------------+----------+--------+-------+----------+
| | _°C._ | _°C._ | _°C._ | _°C._ |
| Laghouat | 439 | 476 | 1,135 | 668 |
| In Salah | 641 | 1,027 | 1,455 | 1,121 |
| Ouargla | 570 | 909 | 1,444 | 923 |
| Ft. National | 230 | 470 | 697 | 564 |
+--------------+----------+--------+-------+----------+

The variation in total heat received at the three desert stations may probably be explained partly at least by their differences in latitude and in elevation above the sea, as well as the different relations they hold to the highlands of the northern portion of the colony. Laghouat lies immediately south of the Saharan Atlas, latitude 33°48′, and at an elevation of 780 meters. Ouargla is approximately 200 miles south of the mountains, latitude 31°55′, and altitude 150 meters. In Salah is in the midst of the western Sahara, latitude 27°17′, and about 300 meters above the sea. Fort National lies in the Tell about 30 miles from the sea, and at an altitude of 916.3 meters. The latitude of Fort National is 36°38′.

There are no published records of the soil temperatures of southern Algeria. In the following table is given soil-temperature data taken at Ghardaia by M. Buret. Maximum and minimum standard chemical thermometers were used. They were placed in a horizontal position in fixed tubes which were about 30 cm. in length. Precautions were taken to properly insolate the instruments. The depth was 15 cm.

TABLE 12.—_Soil and air temperatures, Ghardaia, July_ 2-11, 1911.

+---------+---------------------+---------------------+
| | Soil. | Air. |
| Date. +----------+----------+----------+----------+
| | Maximum. | Minimum. | Maximum. | Minimum. |
+---------+----------+----------+----------+----------+
| | _°C._ | _°C._ | _°C._ | _°C._ |
| July 2 | 36.0 | 31.0 | 41.0 | 21.0 |
| July 3 | 36.0 | 31.0 | 41.0 | 22.0 |
| July 4 | 36.0 | 31.0 | 41.0 | 23.0 |
| July 5 | 36.5 | 31.5 | 41.0 | 23.5 |
| July 6 | 33.7 | 32.0 | 41.0 | 25.0 |
| July 7 | 36.0 | 32.5 | 40.0 | 26.0 |
| July 8 | 36.0 | 32.5 | 38.0 | 26.5 |
| July 9 | 37.0 | | | 25.0 |
| July 10 | 37.0 | 32.5 | 40.0 | 24.0 |
| July 11 | | 33.0 | | 23.0 |
+---------+----------+----------+----------+----------+

An examination of the meteorological reports for Algeria shows that the direction of the prevailing winds varies considerably, although the variation is possibly greater near the coast than in the interior. The winds undoubtedly play an important rôle in the environment of the vegetation of the country. At Algiers, in 1907, winds were reported from the north 288 times, from the east 203 times, from the west 224 times, and from the south 51 times. At Barika, on the High Plateau, the number of times and the directions of the winds for the same year are as follows: northeast, 203 times; east 242; south 21, west 89, and southwest 93. At El Golea, on the desert, the winds were as follows: north 192, northeast 614, southeast 107. The winds from the north, or northerly winds, are cool and laden with moisture, but they are most effective in regions near the coast or in the mountains. Winds from the south are dry winds, and are probably of great importance in limiting the distribution of plants through the increased aridity caused by them.

The most important of these desert winds is the sirocco, a wind that is most likely to blow in spring and summer, although occurring in autumn also, and to a very limited degree in the winter season. The sirocco crosses the Mediterranean and is felt in the southern portions of France, on the Italian Riviera, and in other parts of southern Europe. It is especially common on the High Plateau; for example, during five years it was reported on an average of 28.4 days each year. It does not generally last more than three days, but at Batna, in July, 1902, it was recorded on eight consecutive days. The sirocco operates to lower the relative humidity and to raise the temperature. For instance, on the first day of the eight-day sirocco above alluded to, the average relative humidity was 16 per cent, while the average on the preceding day was 25.6 per cent. It has already been remarked that on the days of the greatest temperature variation the sirocco was usually blowing. In the desert the winds often bring with them much dust and sometimes last during several days; for example, one is reported at In Salah, in May, 1904, for six consecutive days. Such winds on the desert may come from the north, or at least may be northerly, and when storms of this character are in progress, although possibly destructive of animal life or at least comfort, the effects as regards decreasing the relative humidity and raising the air temperature are not so marked as is the case when the sirocco is blowing.

=SOME CHARACTERISTICS OF THE VEGETATION OF THE TELL.=

Because of the similarity in the flora of Algeria and southern Europe, a very good introduction to Algeria is by the way of southern Spain, France, or Italy. As one approaches southern France, for instance, he begins to see evidences of increasing aridity. Upon passing Lyons grassy fields and heavy forests are left behind, the hills become bare or covered with a chaparral-like growth, and the practice of irrigation is observed on the plains. The vegetation, especially of the region between Avignon and Nimes, recalls that of portions of California, and one sees the mulberry, the olive, and the pomegranate in abundance, and occasionally the orange. Very much the same conditions greet one when he arrives in Algiers, except that along the littoral, at and in the vicinity of Algiers, there is a wealth of native and especially of introduced plants, which give little hint of the arid regions close at hand. The hills which make a part of the beautiful city of Algiers contain fine plantations of foreign trees, such as eucalyptus, conifers of various species, acacias, figs, and a variety of fruit trees like the apricot, peach, plum, apple, almond, orange, and others. In the fine public squares one sees large palms also, and in the botanical garden are bamboos, palms, bananas, India-rubber trees, and a large number of forms from the subtropics. The great variety of introduced plants which appear to thrive on the littoral again recalls portions of California, where the kinds and numbers of introduced plants which grow well are likewise large, and where the floral strangers are gathered from the antipodes. But among the species there are also many natives to the colony and which one will see when he begins to travel away from the coast; for example, the cedar from the higher mountains (_Cedrus atlantica_) and the fine pine (_Pinus halepensis_) from lower altitudes; there are junipers and oaks, among the latter the cork oak (_Quercus suber_), and fine specimens of _Pistacia atlantica_ and its protector the jujube (_Zizyphus lotus_), the relationship of which will be given later in this paper. Both of the last-named species are native to the Sahara and are of rather frequent occurrence in the regions visited.

Upon leaving Algiers one soon encounters a striking change in the character of the vegetation, evidences of a rather small rainfall and a low humidity, and one appreciates the fact that even near the coast the climate of the colony is fairly arid. A fine general view of the region about Algiers, giving at a glance its setting and these features, is to be had from the heights behind the city. In the words of Tristram (The Great Sahara):

Here we turned to observe the magnificent panorama of the city and the harbour below, with the bay stretching far beyond, the slopes of Mustapha on the right studded with villas, the Sahel range terminating beyond the massive tower of the seminary of Kouba, the conspicuous Maison Carée . . . planted where the plain of the Metidjeh opens to the sea, the range of the lesser Atlas in the distance beyond, and the peaks of the Djudjura, the last stronghold of the Kabyles, behind them, capped with snow.

Crossing the plain of the Mitidja (Metidjeh), the route runs through a country devoted largely to the raising of wine grapes, with bare hillsides, or hills covered with low shrubs and small trees, and, following a custom derived from France, with either side of the highway lined with trees, mulberry and ash. At the base of the Atlas we see large orange-groves and numerous fig trees. The lower slopes of the mountains are covered with a chaparral-like growth, and as one penetrates the mountains, ascending gradually alongside the Oued Chiffa, he sees, among other forms, extensive areas of dwarf palm, doum (_Chamærops humilis_), which resembles remotely the familiar saw-palmetto of the southern portion of the United States. The leaves of the doum are gathered by the Arabs for making into baskets, rope and other useful articles, and several donkeys laden with doum bales were observed being vigorously driven marketward by their small bournoused masters. On the sides of the gorge one sees species of delicate ferns, bunch-grass in tumbling masses (very luxuriant where there is moisture), chestnut, arbutus, and masses of evergreen ivy overhanging the way in places. At one place, fairly high in the mountains, a colony of native monkeys has found a safe retreat and may be frequently seen gamboling among the rocks and the shrubs near the stream. They were seen and described by Tristram about 50 years ago, who states that they “are of the same species as those of the rock of Gibraltar.” Here are a few oaks, myrtles, some “dherou” (_Pistacia_ sp.), and a few and scattering specimens of _Pinus halepensis_. The upper portion of the mountain, at least of the part seen, is nearly treeless, and is under some cultivation. After leaving the pass a drive of a few minutes brought us to the old Roman town of Medea, which appears from the character of the vegetation, both native and introduced, to have a cooler as well as drier climate than Algiers. Conspicuous among the ornamentals are the Judas tree and the plane, both planted much about the town; among the fruits the apple is cultivated extensively.

From Medea to Berrouaghia the mountain range is broken up into large rounded hills, in part cultivated, but almost wholly open, scantily covered with shrubs or trees and mainly grazed over by large flocks of sheep and goats. About midway between the two places we pass through an open forest of oaks, from whose boles the bark has been removed. A chance acquaintance told us that the cork was removed about once in four years, but this is probably not the true cork oak (_Quercus suber_), which grows under more moist conditions, as between Tunis and Constantine, or between the latter place and Algiers, along the littoral. The altitude of this region is somewhat under 4,000 feet.

From Berrouaghia to Boghari, which is on the northern edge of the High Plateau, the route runs through an open grazing country, with scattering oaks (_Quercus ballota_), juniper (_Juniperus oxycedrus_), and “dherou” (_Pistacia lentiscus_), and, among other herbaceous plants, not a little bunch-grass, whose species I did not learn. On the northern slopes of Mount Gorno, 3,500 feet, is an open forest of oak of the species named, the formation recalling the chaparral of California. Upon reaching the crest of the mountain one is suddenly brought to a forest of pine (_Pinus halepensis_) which covers the entire southern slope to the exclusion of other species of trees. Spreading over the slope on the upper levels, it avoids the gulches near the base and reaches out on the crests of the ridges for a considerable distance. The width of forest where crossed is about 50 kilometers. In its habitat, which comprises the lower Atlas Mountains, _Pinus halepensis_ forms a rather small tree, shapely, with rounded summit. When growing somewhat apart from its fellows it is of a more squat appearance than when in the forest, although the forest of the species is by no means a dense one.

=THE FORESTS OF ALGERIA.=

There are estimated to be between 5,000,000 and 8,000,000 acres of forested land in Algeria. Although the forests lie mainly in the Tell, certain species, notably _Pinus halepensis_, occur in the Saharan Atlas as well. Trees also grow along the oueds, especially on the High Plateau, but not in sufficient abundance to constitute forests proper. The leading species are, among the conifers, _Cedrus atlantica_ and _Pinus halepensis_. The junipers are of importance mainly as a fuel, but do not form forests. Three oaks, namely, _Quercus ballota_, _Q. suber_, and _Q. lusitanica_, are forest-making species, but several other common forms, such as the olive, the plane, the ash, and the betoum (_Pistacia_), may share in the making of a mixed forest, but do not occur in sufficiently large numbers each to constitute a forest. In 1908 in the civil domain the acreage of the leading kinds of forest trees was as follows: oak, 1,853,520; pine (_Pinus halepensis_), 1,398,470; juniper (about one-half being _Juniperus communis_), 444,780; and _Cedrus atlantica_, 85,000.

The species of trees are distributed in well-defined zones, because of which they may to a large degree be segregated, or at least the specific composition of the forest, if a mixed one, may be determined. In altitudinal range, the oaks are found from sea-level to 6,000 feet, within which each species may have its characteristic range. For example, _Quercus suber_ reaches from sea-level to 2,500 feet; _Q. ballota_ from 2,500 to 4,000 feet; and _Q. lusitanica_ from 3,500 to 6,000 feet. _Pinus halepensis_ grows from the sea-level to 3,600 feet, and probably much higher in the Saharan Atlas, while _Cedrus atlantica_ is to be found from 4,000 to 6,000 feet. _Abies barborensis_ is said to attain a higher altitude than the cedar.

Among the definitive physical factors by which the composition of a forest is determined—the rainfall, the temperature, the soil, and the altitude—probably of the first rank should be considered the rainfall and the temperature, which are affected by the altitude. In the case of the distribution of the cork oak, however, the character of the soil plays an important rôle. This species grows only on sandy soil, and where the rainfall exceeds 600 mm. Because of the latter requirement the larger part of the cork-oak forested area is east of Algiers, the annual rainfall to the west of that place falling for the most part under 600 mm. Similarly the minor features of distribution, inside of the specific range, may be explained. For example, in the upper limits of its range, _Pinus halepensis_ appears chiefly on southern slopes, as on Mount Gorno, while at the low altitudes it is to be found on the northern face; temperature reactions apparently—familiar phenomena in mountainous districts.

Because of the unison of response to common environmental factors, much of the forested area, especially at the higher altitudes, is composed of one species or one species largely predominates. This is true of the pine and the cedar forests to a marked degree; _e.g._, in the pine forests on Mount Gorno and the cedar near Batna.

Commercially speaking, the cork oak is at present the most important species in Algeria. It occupies about 600,000 acres, and the yearly yield is valued at nearly $1,000,000. It may be seen along the railroad between Tunis and Constantine and east of Algiers. When old the species has a peculiarly gnarled appearance, with a short, stout bole, usually hollow, which may become 10 feet in diameter, with irregular, straggling branches. It is less symmetrical in nature than under cultivation, as in the Santa Clara Valley and Santa Barbara, California, where a few specimens may be found. Another species of oak, _Quercus ballota_, of no great commercial importance, provides the source of the acorns in general use among the natives for food. The acorns are found in all markets, even (as in Ouargla and Ghardaia) where transportation for considerable distance is necessary; they are less astringent and hence more pleasant than those of most species. Although _Q. ballota_ appears not to be planted for its fruit, it has been stated (Kearney and Means, _loc. cit._) that the Kabyles preserve such selected trees as have superior fruit, which would perpetuate the best-liked varieties. It may be remarked in passing that the seeds of the pine are also in common use among the Arabs as a food, although not employed so generally nor in so many ways as the acorn.

The cedar (_Cedrus atlantica_), the most beautiful tree in Algeria, is found in high altitudes only and on mountains separated from one another, but always in the more northern Atlas ranges. In the following mountain groups are to be found the main cedar forests, namely: Ouarensis, Teniet, Blida, Babor, Maadid, and the Aurés. The forest seen was that near Batna, near the western base of the most important range in Algeria, the Aurés. Somewhat below the lower limit of the Batna cedar forest is an open forest of oaks (_Quercus mirbeckii_), _Juniperus oxycedrus_, and _J. phœnicea_, mingled with which are shrubs suggesting those of the desert, such as _Acanthyllis numidica_ and _Retama sphærocarpa_, as each genus is represented south of the Saharan Atlas on the open desert. These species are mainly confined to the southern facing, and hence on the side of the mountains opposite the beginning of the cedar. By the roadside are to be seen also several specimens of _Juniperus oxycedrus_ badly infested with the mistletoe (_Arceuthobium oxycedri_). In one instance the unusual condition was observed of a mistletoe group remaining alive on a host branch which appeared to be dead for several inches below the point of attachment.

The first representatives of the cedar forest were encountered as stragglers in the dry wash at the north base of the mountain on which the forest is situated. In part these trees were shapely, with a taper summit, and in part they were short, with a summit broad and flat, in effect like an inverted cone. When the main forest was entered the trees were mainly of the type first characterized, with widely reaching lower branches and slender summits. In exposed places or in older parts of the forest the trees of the second type were often seen; and on the crest of the mountain the most bizarre shapes (induced by wind action), the trunks nearly parallel to the ground and the branches hugging the ground. In the upper portion of the forest the trees were more widely separated than in the lower portion, and here and there we met with really large specimens, which must have been very ancient. One of the large trees had a bole which 1 meter above the ground was about 5 meters in circumference. The trees were fruiting freely, but we did not see many seedlings. Why, was not apparent. There were no indications that fires had swept over the mountain recently.

=THE HIGH PLATEAU.=

The vegetation of the High Plateau, taken as a whole, is sparse, due in part to rather light annual precipitation, but largely to the lack of efficient drainage, for which reason large areas are so heavily charged with salts as to be inimical to most plants. Halophytes form an important element in the flora of this region. In the most intense salt areas no plants are to be found at any season. Along the oueds such shrubs as species of _Tamarix_ and _Zizyphus_ occur, and juniper may be seen in the more elevated places, such as near Guelt-es-Stel or further toward Djelfa.

The route followed across the High Plateau ran from Boghari to Ain Ossera, Guelt-es-Stel, and Djelfa, which is in the midst of the Saharan Atlas, and from thence to Laghouat.

=BOGHARI TO LAGHOUAT.=

Boghari, situated at the place where the Oued Chelif, having come across the High Plateau, enters the Tellian Atlas on its way through them to the Mediterranean, lies on the northern edge of the High Plateau and in what appears to be a fairly arid region. The oued at this place is rather narrow and has low banks. In its bed, in October, were a few pools of water. On either side is the flood-plain of the oued, several meters in width, sometimes partly under cultivation. Tilled fields are to be seen to the west and not far from the town. From the low mountains immediately to the west of the town the steppes stretch unbroken (save by low hills) to mountains bounding the southern horizon, possibly 100 miles straight away. The mountains are the Dj. Sahari, the Saharan Atlas, beyond which lies the desert.

The vegetation in the neighborhood of Boghari is at present meager in amount and of small size. Along the banks of the Chelif are a few tamarisks, and on the plain not far from the oued are a few specimens of _Zizyphus vulgaris_ and _Pistacia lentiscus_ and other low-growing shrubs. Owing to the large number of sheep, goats, and camels which are driven through the pass of the Chelif, or which are kept in the neighborhood by their Boghari owners, few plants thereabouts fail to exhibit indications of being eaten. In fact, at Boghari the effects of grazing were first noticed, though afterwards repeatedly seen. Only such plants as are poisonous, distasteful, or heavily armed survive the predatory attacks of the countless numbers of domestic animals.

The habitat of _Pinus halepensis_, which thus extends to the very edge of the steppes, is to the east and west of the town. To the west it forms an open forest and is associated with _Quercus ballota_, growing on the crest and on the northern slopes of the low mountains. Its abundant fruit, together with acorns, is gathered assiduously by the Arabs for food. _Juniperus oxycedrus_ and _J. phœnicea_ also occur.

After leaving Boghari and the plain by the Oued Chelif, the route goes among low, rounded hills for a distance of about 24 kilometers, when it strikes boldly across the wide-extending plain. The general appearance of the vegetation, away from the intensely salty chotts, is that of low-growing shrubs on the plain, and of somewhat higher shrubs or low trees along oueds. Of the former, perhaps the most abundant are _Noæa spinosissima_ and _Haloxylon_ sp., and by the oueds _Tamarix_ sp. and _Zizyphus_ sp. Near Ain Oussera is a wide belt of _Stipa tenacissima_, the alfa grass, which occurs nearly to the exclusion of other species, and a second belt of alfa, several kilometers in width where crossed, was seen very soon after leaving Guelt-es-Stel. At each of these places were seen large piles of the grass baled ready for hauling to Algiers.

The alfa, or bunch-grass, covers large areas in Algeria as also in Spain. In November the long leaves of the grass are dry, tightly rolled, and rush-formed, in place of being flat as during the rainy season or period of growth. The species reproduces largely by means of much-branched rhizomes, from which spring the young, fleshy leaves, enlarged at the base. In Algeria, “situées en territoire civil,” there are 543,620 acres of alfa, mostly on the High Plateau, but a part along the littoral in the province of Oran, west of Algiers. The leading environmental influence upon the peculiar distribution of the species is apparently that of rainfall, reacting in this respect very like plants with storage organs, avoiding alike regions where the rainfall is excessively heavy or where it is so little as to cause marked desertic conditions. It is apparently confined to sandy soils and is replaced by others wherever the soil of a region (otherwise appropriate for its growth) is of clay or is charged with any considerable amounts of salts. It is an important article of export from Algeria. Its total tonnage is said to amount to 80,000 each year, bringing approximately $1,500,000. It is sent to England, Belgium, and France, and used in the manufacture of fine grades of paper, light, strong, and of a silky texture; also in making baskets, hats, and mats, for which a superior grade of the grass, commanding especially high prices, is employed (Kearney and Means, _loc. cit._).

Among other species commonly seen in crossing the steppes are various salt-bushes, such as _Haloxylon articulatum_ and _Anabasis articulata_ and especially _Artemisia herba-alba_, with _Tamarix_ and a few specimens of _Pistacia_ along the oueds or where water conditions are most favorable. Between the belt of alfa last mentioned and El Masserane, a bordj, there is a broad plain surrounded by low mountains, which are really the northern extension of the broad Saharan Atlas, where salt-bushes occur in a formation several kilometers, possibly 24, across. Here in the summer the nomads, coming up out of the desert, find grazing for their flocks, and even in October we saw countless numbers of sheep and goats, and hundreds of camels, browsing the shrubs.

At El Masserane are specimens of large _Tamarix_, really the size of small trees, growing near the bordj; and to the south of the bordj we passed the first dunes encountered on the plateau. These are part of a series of dunes which were seen to extend to the horizon to the northeast, as we approached El Masserane, and which, we were informed, reached as far as Bou Saada, nearly 90 kilometers distant. The dune flora was quite different from that of the surrounding plain, owing to the total absence of salt plants, and to the presence, among other species, of a _Tamarix_ and a large grass, the “drinn” (_Aristida pungens_), which was subsequently frequently seen.

Soon after passing the dunes the way lay through a country with low mountains, almost bare of vegetation, where scattering oaks and junipers constitute the only species of plants, until we reached the walled town of Djelfa.

=DJELFA TO LAGHOUAT.=

The bleakness and the bareness of the environs of Djelfa come with a surprise when one considers that the rainfall of the place is not inconsiderable, about 375 mm., and that the altitude is about 1,110 meters, which insures a fairly low temperature and hence a relatively low evaporation rate. The sparseness of the vegetation is probably partly due to the fact that the rainfall does not occur at one or at two seasons, as nearer the coast, but is distributed fairly evenly between the four seasons, and also to the long occupancy by the Arabs and the French, by which possibly most of the useful native plants, large and small, have long since been destroyed. Somewhat removed from the town, particularly on the mountains to the west, is a forest of pines. Along the streets are many shade trees, as Lombardy poplar, ash, locust, and others, and within the town limits is a small but fine public park and experimental garden with a large variety of shrubs and trees.

From Djelfa to Laghouat the road runs through barren mountain passes, and is dreary and of little interest. Tristram’s description of the approach to Laghouat, written about 1860, gives very well the present condition of things:

The next day’s journey was through a rocky desert country. . . . We afterwards passed a low-lying strip of sand-hills on the west, with the marks of an ancient ocean beach; on the east a high range of mountains, with the stratification regular and horizontal. . . . Our next day’s ride was by a base of a continuous chain of steep ridges, again with an even water-line very near the crest, and presenting a singular serrated appearance (the Djebel Lazareg). I counted no less than 127 little peaks rising above this straight horizontal line, almost all of them of equal height, like the crests of a long sea-reef; and lower down the sides were many tidal strings, if I may so term them. Turning around to our left and crossing the dry channel of an evaporated and aged “Wed,” we had some low headlands close behind us—Ras Ainyah of the Arabs, “Prise d’eau” of the French—the scene of a bloody combat under General Yusuf. Through an opening between the mountains we debouched on a wide plain, and suddenly before us stood an isolated rock. Two cliffs facing each other bore each a bastioned tower, and in a depression between these lay a town.

The town, whose situation is thus so graphically presented, is Laghouat, of which the leading present interest lies in the fact that it is on the very edge of the Sahara proper. From the rocky hills by the town one can see the serrated Saharan Atlas to the north, extending northeast and southwest, and, turning, to the south, an expansive and gently undulating bare plain, stretching without a break to the horizon.

=LAGHOUAT.=

The ancient Arab town of Laghouat, which is also an important military post, is a very favorable place from which to begin a study of the plants and the environment of the plants of the northern Sahara. Its altitude (780 meters) is greater than that of Ghardaia (520 meters), as also that of the latter place is greater than the altitude of Ouargla (150 meters). The annual rainfall of Laghouat is more than that at either of the places mentioned and more dependable. The surface of the desert at Laghouat is, for example, not of one type only, but characteristic of much of the Sahara; that is, it is mainly stony, a hamada, but there are also sand areas, a oued and its flood-plain. Finally, the plants growing in the vicinity of Laghouat are largely typical of those found farther to the south, as at Ghardaia and Ouargla, or even deeper in the desert. It is of great interest to observe the change in the habits of the plants, in their number, distribution, and other features, when one leaves a less arid region and goes toward a region of gradually increasing aridity, as when passing southward from Laghouat.

The leading plant habitats are the oasis, the arid plain, and the dunes. It is not likely that any of these habitats have been greatly changed because of the settlement by Arabs. The arid plain and the dunes surely have _per se_ not suffered marked alteration, and the oasis itself is probably not so different from what it was formerly, as the great difference in plants growing in it might at first lead one to suspect. More water is brought to the surface at present than in primitive times, but if it were possible to remove all introduced plants, and restore all native plants peculiar to the oasis, there is no apparent reason why they should not live there quite as successfully as in earlier times. It does not follow that there has been no modification of the flora itself, a result of the founding of a town at the oasis, and it will be pointed out later that such has surely been the case, but to what extent or in what way does not appear.

THE OASIS OF LAGHOUAT.

The oasis of Laghouat is situated on the Oued Mzi, the upper portion of the Oued Djedi, one of the most important oueds of Algeria. The Oued Djedi runs in an easterly direction from Laghouat, receiving many tributary oueds _en route_, by a rather long course to the great Chott Melrirh, which is southeast of Biskra. Like other desert rivers, the Oued Djedi is dry most of the year, but is occasionally filled to overflowing with a rushing flood, which is of great erosive power and may be very dangerous to the traveler. Above the town of Laghouat, where the Oued breaks through the last pass of the Atlas, the flood-plain is narrow, but upon leaving the pass the plain widens until in the immediate proximity of the town it is about 1.5 kilometers in width. On either side of the flood-plain stretches the arid plain (hamada), usually stony, but near the mountains covered with low, slowly moving sand ridges. To the south of the oasis, the arid plain merges into the topography characteristic of the region of the dayas.

The portion of the oasis devoted to the cultivation of date and other trees, and to gardens, is about 3 square kilometers in size, but arable land extends above and below the town, so that outside of the oasis, as delimited above, there are about 6 square kilometers, all of which have at times been under cultivation. The last referred to is the flood-plain of the oued and is used mainly for growing barley. By the edge of the oued, or along the irrigating ditches, are several characteristic species of plants, which may point to the character of the primitive flora; for example, willows, oleander, and _Tamarix_, with a few palms. The betoum (_Pistacia atlantica_), which must surely have been an inhabitant of the oasis formerly, is now apparently wholly absent. The species just mentioned are to be found between the town and the pass above; but below the oasis, owing to an apparently poorer water-supply, there are fewer large species. Among those found are a few specimens of _Rhus oxyacantha_ and _Zizyphus vulgaris_, and it was probably below the town that the betoum was to be found in earlier times.

The oasis is under intensive cultivation (see fig. 1). There are about 300 gardens, each bounded by mud walls, and often separated by picturesque, meandering lanes. The plant life, almost wholly introduced, is luxuriant. In some gardens the effect is tropical, where vines reach from tree to tree, making a canopy nearly sun-proof and separating the spreading tops of the palms from the wealth of shrubbery and herbaceous plants beneath. First among the trees of the gardens, in numbers as well as in economic importance, is the date palm, of which there are said to be about 30,000. Although this is small in comparison to the number of date palms at Ouargla, Touggourt, or the Oued Rirh, the dates are of great importance to the dwellers at Laghouat, where the products of the gardens are almost all consumed. The living tree provides shelter against the intense heat and light of the desert, and the dead leaves constitute an important source of fuel in a land where fuel is extremely hard to obtain. The flesh of the date fruit is eaten by the Arab and the cracked seeds are given to the camels. Without the date a continuous occupancy of a remote oasis by the Arab is clearly impossible. Besides the date palm fruit trees of other kinds are abundant, among them the apricot, fig, mulberry, peach, pear, and orange. The pomegranate and the table grape are also very generally grown. The lowest story of the vegetation of the gardens is composed of garden vegetables, such as artichoke, bean, carrot, melon, pea, potato, squash, and radish. Among the ornamentals one sees roses, asters, and chrysanthemums, and occasionally very luxuriant cannas. One or two parks contain interesting introduced trees and shrubs. We recognized among the trees _Ailanthus_, _Eucalyptus_, umbrella, plane, poplar, pine, cypress, ash, locust, willow, and St. John’s tree. The Barbary fig (_Opuntia ficus indica_) is also common, but does not stray away from the best-watered situations.

THE PLAIN.

The part of the plain (hamada) studied lies to the west of the oasis, between it and the adjacent hills, Mountains of the Nomads, which are to the west of the pass of the Oued Mzi. Emerging from the oasis, one finds himself on the arid plain, the transition from the one to the other being abrupt. The plain, at first view, with a covering of small stones and pebbles, gives the impression of total barrenness. Not a tree, shrub, or herb appears to hide the bare ground. The mountains are naked rock, while the harsh outline of desert ranges and the distant low sand ridges give no evidence of plant life. But a closer examination of plain, dune, and mountains reveals the presence either of living forms or of the dried remains of plants of a preceding moist season, in numbers and in kinds not at first suspected.

Close to the oasis the plain forms the highway for caravans as well as the drilling ground for army recruits, so that the herbage is either trodden under foot or eaten to the roots. Somewhat farther away, where the plain rises to meet the mountains, we first encounter perennials large enough and abundant enough for consideration, the most prominent being quedad (_Acanthyllis tragacanthoides_), adhidh (_Zollikoferia spinosa_), rempt (_Haloxylon articulatum_), and drinn (_Aristida pungens_); _Acanthyllis_ is perhaps the most numerous.

Quedad is the most striking plant native to Laghouat. It is a shrub, related to _Astragalus_, usually not over 40 cm. high. A single specimen consists of a group of unbranched or little-branched stems, rather stout, of a grayish-green color, and provided with long and stout spines. As a whole the plant has a very close resemblance to small specimens of ocotillo (_Fouquieria splendens_) of the southwestern United States. During dry seasons the stems are bare, but when the rains return leaves are put out in the axils of the spines, which are the rachides of the leaves. The habit of quedad is shown in figs. 4 and 6. Although the species is so well protected against attack by animals that it rarely, if ever, suffers on that account, it is made a supplemental food through the burning off of the spines. When thus prepared the half-woody stems are eaten with avidity by camels.

The census of _Acanthyllis_ was taken on the upper portion of the arid plain at a place where the plant seemed to be most abundant. On an area 16 by 16 meters, 92 specimens were found living. This was the dominant species. Other species, present in less number, were so badly eaten by animals as to be quite unrecognizable.

The root-system of _Acanthyllis_ offered some points of interest and a short study of it was made in the field. All of the specimens whose roots were examined were growing in the habitat above referred to and within a meter of one another. The leading results of the observation are as follows: The largest specimen studied possessed a tap-root 3 cm. in diameter at the crown. Growing rapidly smaller as it ran downward, the root gave off four laterals, of which a portion dipped at an acute angle to a depth of 20 to 30 cm., sending off branches by the way. One of the largest of the laterals was traced 75 cm. and where left was 2 cm. beneath the surface. The branches, at least of the main laterals, that is, the roots of the tertiary order, for the most of their course ran thus near the surface of the ground. One of the leading laterals was followed to the base of a neighboring specimen of quedad, where it lay close to the crown of the main root. The depth of the penetration of the tap-root of this specimen was not learned. The tap-root of a neighboring specimen ran directly downward 20 cm.; then, turning sharply, it extended in a horizontal direction for a distance of 70 cm. As the large laterals were wholly lacking on this plant, the tap-root was the entire system—surely an anomalous condition. On a third plant the tap-root penetrated the ground about 4 cm. only, after which it turned and ran the rest of its course within 4 cm. of the surface. The more superficial of the roots of a fourth specimen were found to extend to the base of the last plant mentioned. Thus it was found that the root-system of _Acanthyllis_, as growing naturally, extends both widely and deeply for a considerable distance, and that it is flexible to a degree; in short, is generalized[8] and closely resembles that of certain species of the Tucson region, particularly _Covillea tridentata_, which grows under similar conditions.

The root-systems of three or four other species were also examined. Of these _Zollikoferia spinosa_ and _Artemisia campestris_ were growing in a little hollow in the plain close by the habitat of _Acanthyllis_. _Zollikoferia_ has a very close habit of growth with dichotomous branching (compare figs. 5 and 7). When dry the branches are slender and of a woody hardness. The root-system of this species is characterized by a pronounced tap-root and by the absence of large laterals, at least near the surface. The leading feature of the root-system is, in short, its tap-root. A root-system of a similar type was found in _Artemisia herba-alba_.

Rempt (_Haloxylon articulatum_) also occurs on the plain. This is a shrubby perennial (half shrub?) which is possibly the most often met of any species, or at least genus, in southern Algeria. It is capable of enduring very arid conditions, is unarmed, and is much eaten by all herbivorous animals. The plant will be figured and especially referred to later in this study, so that at this time only a brief definition will be given of its root-system, which is a typically generalized one, penetrating the ground fairly deeply if the character of the soil permits, but also lying near the surface; there is also a relatively large number of secondary and tertiary roots, characteristic of the generalized type.[9]

Inspection of the soil showed it to be a sandy clay with a large percentage of pebbles and stones and with greater depth of earth in the hollows on the plain than on low ridges. It probably contains some gypsum, since an outcropping of it occurs on the southern face of the low mountains to the north. Taken as a whole, the soil appeared very like that of the plain by Tilrempt and Ghardaia, as well as between Ghardaia and Ouargla (Gantara). The soil will be described later in this paper.

THE DUNES NEAR LAGHOUAT.

Dunes are not present in large enough numbers, or of large enough size, to figure very prominently in the topography of the environs of Laghouat; but they occur both to the east and to the west of the town, those to the east being the larger. Sand is found facing the south side of the Rocher des Chiens, a rocky hill on the western edge of the oasis, and the south side of a portion of the Nomad Mountains, to the north. There is also a succession of low dunes between the Nomad Mountains and the oasis. The Rocher des Chiens dune is moving from west to east, but the dune along the face of the Nomad Mountains is probably stationary. The series of dunes on the plain are moving toward the northeast.

An inspection of the dunes shows that the number of individuals, as well as the number of species, is very limited. In fact there are apparently fewer plants here than on the dunes of large size subsequently encountered between Ouargla and Touggourt. The most characteristic plant is “drinn” (_Aristida pungens_), but it is by no means common; there are also a few specimens of _Tamarix_ growing near the Nomad Mountains. As frequently happens where there are moving dunes, the passage of the dune greatly changes the character of the flora. Although this feature was not especially studied, it was noted that the number of grasses where the dune had swept was greater than it was before this. _Acanthyllis tragacanthoides_, a plant typical of the plain, was found to survive the passage of the sand, although changed in appearance in a characteristic manner. It will be recalled that the species has a top consisting of several shoots, springing from the root-crown at the level of the ground, and a root-system in which the laterals and the main root are alike well developed. In order that a plant, already established, can maintain this general relation during the heaping up of the sand, the main root must grow at the crown as fast as the sand encroaches. This is exactly what happens, so that, when the dune has passed on, the shoot of the species is elevated for a space equaling the depth of the sand, which is half a meter or more. From the probability that _Acanthyllis_ is of very slow growth and that the dunes are low, it follows that the rate of dune movement must be slow.

THE MOUNTAINS ABOUT LAGHOUAT.

The southern spurs of the Saharan Atlas lie to the north of Laghouat, within 3 miles of the oasis. This range (the Nomad Mountains) is not over 266 meters in height. Higher mountains extend both to the west and to the east, but only the Nomads are visited. There are also two high, rocky hills on opposite edges of the oasis, the town lying between, and it is perhaps because of their presence that the water is forced to the surface, or near the surface, and the oasis is formed. The hill to the west of the town is called the Rocher des Chiens. On the south side of the Nomad Mountains is a long outcropping of gypsum; the south face of these mountains is also abrupt, carrying little soil; but on the northern face the slope is gradual and there is much soil, although rocks are abundant.

Two localities only in the Nomad Mountains were seen. One was in a pass through which caravans travel _en route_ to Laghouat, from the High Plateau or the more distant Tell; the second to the east of the pass is much less often visited by flocks. The physical plant conditions appeared to be the same in both locations. As one approaches the mountains from the south the number of plants grows less until on the south face they quite disappear, but on attaining the crest they quickly increase and form a noticeable element in the landscape. In fact, the flora of the northern gentle slope, where the soil conditions are relatively favorable, is much richer than on the plain or the dunes. Had the shrubs been of good size they would have been very conspicuous.[10]

A certain area on the north slope of the Nomad Mountains, not far from the pass through which the Oued Mzi goes, was selected for making a census of the plant population. Here the number of individuals, as well as their size, showed that the moisture relations were good as compared with those of the plain. On an area 16 meters square 422 living perennials were found, mainly of the following species: _Acanthyllis tragacanthoides_, _Asparagus spinosa_, _Deverra scoparia_, and _Zollikoferia spinosa_. The most numerous, _Zollikoferia_, was represented by 96 individuals. The general character of the habitat and the plants is sufficiently well shown in fig. 8 and does not need further mention in this place.

EFFECTS OF GRAZING ON VEGETATION NEAR LAGHOUAT.

It is generally recognized that a potent influence is exerted by man, and the lower animals, in shaping the flora of an arid region, not only as regards the kind and number of plants, but also as concerns certain of the leading characteristics of the plants themselves. The action is largely such as brings about a survival of the “useless” forms, so that we do not know, from the plants we meet in the desert to-day, how many or what kinds of plants it might support. It also may be true that no desert shows the modifying effects of the causes suggested more than the northern Sahara.