Chapter XXIV: Appendix: G (2)

+---------------+-----------+-----------+-----------+-----------+
| | | Middle | Superior | Sierra |
| | Gt. Atlas | Zone, Gt. | Zone, Gt. | Nevada, |
| | valleys. | Atlas. |Atlas. 176 |&c., above |
| | 455 sp. | 341 sp. | 176 sp. | 800 m. |
| | | | | 890 sp. |
+---------------+-----------+-----------+-----------+-----------+
|Dicotyledones | 391 86·0| 286 83·9| 154 87·5| 762 85·6|
| | | | | |
|Monocotyledones| 64 14·0| 55 16·1| 22 12·5| 128 14·4|
| | | | | |
|Compositæ | 63 13·8| 46 13·5| 22 12·5| 119 13·4|
| | | | | |
|Leguminosæ | 48 10·5| 38 11·1| 14 8·0| 67 7·5|
| | | | | |
|Gramineæ | 39 8·6| 37 10·8| 14 8·0| 59 6·6|
| | | | | |
|Caryophylleæ | 26 5·7| 14 4·1| 15 8·5| 40 4·5|
| | | | | |
|Cruciferæ | 25 5·5| 7 2·1| 21 11·9| 49 5·5|
| | | | | |
|Labiatæ | 23 5·0| 18 5·3| 11 6·3| 54 6·1|
| | | | | |
|Scrophularineæ | 21 4·6| 13 3·8| 10 5·7| 37 4·2|
| | | | | |
|Umbelliferæ | 20 4·4| 16 4·7| 5 2·8| 50 5·6|
| | | | | |
|Rubiaceaæ | 18 4·0| 15 4·4| 7 4·0| 20 2·2|
| | | | | |
|Papaveraceæ | 10 2·2| 8 2·3| 3 1·7| 10 1·1|
| | | | | |
|Geraniaceaæ | 10 2·2| 8 2·3| 4 2·3| 10 1·1|
| | | | | |
|Liliaceæ | 10 2·2| 6 1·8| 4 2·3| 15 1·7|
| | | | | |
|Boragineæ | 9 2·0| 5 1·5| 6 3·4| 18 2·0|
| | | | | |
|Ranunculaceæ | 8 1·8| 5 1·5| 4 2·3| 28 3·1|
| | | | | |
|Cistineæ | 7 1·5| 6 1·8| 1 0·6| 23 2·6|
| | | | | |
|Rosaceæ | 7 1·5| 4 1·2| 3 1·7| 26 2·6|
| | | | | |
|Campanulaceæ | 6 1·3| 5 1·5| 1 0·6| 9 1·0|
| | | | | |
|Convolvulaceæ | 5 1·1| 5 1·5| 1 0·6| 3 0·3|
| | | | | |
|Coniferæ | 5 1·1| 4 1·2| 1 0·6| 10 1·1|
| | | | | |
|Saxifrageæ | 4 0·9| 4 1·2| 4 2·3| 12 1·3|
|(inclusive of | | | | |
|Grossulariæ) | | | | |
| | | | | |
|Cyperaceæ | 4 0·9| 4 1·2| 1 0·6| 17 1·9|
| | | | | |
|Gentianeæ | | | | 7 0·8|
| | | | | |
|Primulaceæ | 2 0·4| 2 0·6| 1 0·6| 7 0·8|
| | | | | |
|Junceæ | 1 0·2| 1 0·3| | 11 1·2|
+---------------+-----------+-----------+-----------+-----------+
[**Continued]

+---------------+-----------+-----------+-----------+-----------+
| |Superior[1]| | | Southern |
| | Zone, |Bulgardagh.| Dalmatia. | side of |
| | Sierra | 882 sp. | 2,002 sp. | the Alps. |
| | Nevada. | | | 2,545 sp. |
| | 486 sp. | | | |
+---------------+-----------+-----------+-----------+-----------+
|Dicotyledones | 419 86·2| 808 91·6| 1594 79·6| 2035 80·0|
| | | | | |
|Monocotyledones| 67 13·8| 74 8·4| 408 20·4| 510 20·0|
| | | | | |
|Compositæ | 63 13·0| 97 11·0| 235 11·7| 343 13·5|
| | | | | |
|Leguminosæ | 32 6·6| 93 10·5| 222 11·1| 172 6·8|
| | | | | |
|Gramineæ | 37 7·6| 38 4·3| 173 8·6| 176 6·9|
| | | | | |
|Caryophylleæ | 29 6·0| 81 9·2| 74 3·7| 121 4·8|
| | | | | |
|Cruciferæ | 37 7·6| 84 9·5| 98 4·9| 139 5·5|
| | | | | |
|Labiatæ | 28 5·8| 67 7·0| 100 5·0| 89 3·5|
| | | | | |
|Scrophularineæ | 28 5·8| 39 4·4| 66 3·3| 109 4·3|
| | | | | |
|Umbelliferæ | 23 4·7| 33 3·7| 113 5·6| 113 4·4|
| | | | | |
|Rubiaceaæ | 12 2·5| 19 2·2| 26 1·3| 34 1·3|
| | | | | |
|Papaveraceæ | 6 1·2| 12 1·4| 14 0·7| 14 0·6|
| | | | | |
|Geraniaceaæ | 6 1·2| 6 0·7| 17 0·8| 23 0·9|
| | | | | |
|Liliaceæ | 9 1·9| 23 2·6| 61 3·0| 52 2·0|
| | | | | |
|Boragineæ | 11 2·3| 23 2·6| 40 2·0| 39 1·5|
| | | | | |
|Ranunculaceæ | 15 3·1| 11 1·2| 53 2·6| 87 3·4|
| | | | | |
|Cistineæ | 10 2·1| 1 0·1| 11 0·5| 10 0·4|
| | | | | |
|Rosaceæ | 20 4·1| 21 2·4| 57 2·8| 93 3·7|
| | | | | |
|Campanulaceæ | 6 1·2| 21 2·4| 26 1·3| 46 1·8|
| | | | | |
|Convolvulaceæ | 2 0·1| 4 0·5| 10 0·5| 9 0·4|
| | | | | |
|Coniferæ | 8 1·6| 15 1·7| 15 0·7| 11 0·4|
| | | | | |
|Saxifrageæ | 9 1·9| 2 0·2| 9 0·4| 52 2·0|
|(inclusive of | | | | |
|Grossulariæ) | | | | |
| | | | | |
|Cyperaceæ | 12 2·5| 7 0·8| 43 2·2| 119 4·7|
| | | | | |
|Gentianeæ | 5 1·0| 4 0·5| 14 0·07| 31 1·2|
| | | | | |
|Primulaceæ | 6 1·2| 8 0·9| 12 0·6| 60 2·4|
| | | | | |
|Junceæ | 9 1·9| | 8 0·4| 31 1·2|
+---------------+-----------+-----------+-----------+-----------+

the whole number of phanerogamous species included in the Flora of the region, and opposite the name of each natural order I have entered the number of species found in each region, and the percentage proportion which this number bears to the entire flora. Besides the orders which bear the largest proportion in the Great Atlas Flora I have enumerated those that usually characterise the vegetation of high mountains in this part of the world, though several of these are little, or not at all, represented in the Flora of the Great Atlas.

Confining the comparison in the first instance to the figures given for the Atlas Flora as a whole in the first column, and those given in the fourth, sixth, seventh, and eighth columns respectively, for the Sierra Nevada, the Bulgardagh, Dalmatia, and the southern side of the Alps, we remark in the first place that _Monocotyledons_ bear about the same proportion to _Dicotyledons_ in the Great Atlas that they do in the Sierra Nevada, the percentage here being much larger than it is in the Bulgardagh, and considerably less than in Dalmatia or the Southern Alps. In this part of the world this percentage in the Flora of a given region mainly depends upon the number of _Gramineæ_ and _Cyperaceæ_. The abundance of the latter group in the Alps doubtless arises from the fact that at a former period physical conditions favoured the migration of a large number of northern species that have been unable to extend to the more southern mountain regions of the Mediterranean area.

In all the regions under consideration we find, with a single exception, that the same eight natural orders take precedence of all others as regards the number of species that they exhibit, the aggregate in every case exceeding one-half of the whole phanerogamous Flora. These natural orders are _Compositæ_, _Leguminosæ_, _Gramineæ_, _Caryophylleæ_, _Cruciferæ_, _Labiatæ_, _Scrophularineæ_, and _Umbelliferæ_. The exception arises from the prevalence, already noticed, of _Cyperaceceæ_ in the Flora of the Southern Alps. In comparing the figures in the Great Atlas column with those for the other areas above enumerated, it is well to recollect that our materials are taken from a district much more limited in extent than the others, and are necessarily imperfect, because obtained from a single short visit to each valley at a season when many species are yet undeveloped. It is probable, for instance, that the proportion of _Umbelliferæ_ would be increased if the whole Flora were better known. Subject to this remark, it will be seen, as might be expected, that the constituents of the Great Atlas Flora show more analogy with those of the Sierra Nevada and Bulgardagh Floras than with those of Dalmatia and the Southern Alps; but the proportion of _Compositæ_ is larger than in any of them (nearly 14 per cent). In comparing the vegetation of a small district with that of a large one it must be recollected that a small natural group containing a few widely spread species, such as _Geraniaceæ_, is likely to show a larger percentage proportion to the whole Flora in the small district than in the larger one. It may happen that the same species are spread through both regions; but in one case the number is to be compared with a small total, in the other with a much larger one. This remark has a bearing on the fact that in the Great Atlas Flora the natural orders that bear an unusually large proportion to the total number of the Flora are _Leguminosæ_, _Caryophylleæ_, _Rubiaceceæ_, _Papaveraceæ_, _Geraniaceæ_, and _Convolvulaceæ_. On the other hand, there is a remarkable deficiency in the natural orders that especially characterise the Flora of the Alps, and in a less degree, the high mountains of Southern Europe. These are _Ranunculaceceæ_, _Rosaceæ_, _Saxifrageæ_, _Primulaceæ_, _Junceæ_, and _Cyperaceæ_; not to speak of _Gentianeæ_, which are here altogether absent.

If, instead of regarding the Atlas Flora as a whole, we examine separately the figures given in the several columns for the middle and superior zones respectively, we find very different proportions for the chief natural orders, except for _Compositæ_ and _Leguminosæ_ which are in both very numerous. In the middle region of the Atlas these two orders represent very nearly one-fourth of the phænogamous Flora. After these _Gramineæ_, _Rubiaceæ_, _Papaveraceæ_, _Geraniaceæ_, _Cistineæ_, and _Convolvulaceæ_ are, in the middle region, unusually frequent, while _Cruciferæ_, _Rosaceæ_, _Boragineæ_, and _Liliaceæ_ are remarkably deficient. In the superior zone, on the other hand, the proportion of _Compositæ_ and _Leguminosæ_ is less excessive, making jointly a little over one-fifth of the whole Flora of the upper region. The most marked characteristic here is the very large proportion of _Cruciferæ_, being less by one species only than the number of _Compositæ_. Taking into account the number of individuals as well as that of species, this must be regarded as the dominant element in the Flora of the higher region of the Great Atlas, affording as it does 12 per cent of the whole Flora. The only region in which this characteristic is approached is the Bulgardagh in Cilicia, where _Cruciferæ_ supply near one-tenth of the whole list. _Caryophylleæ_ also form an unusually large element in the Flora of the upper zone of the Atlas; but, unlike _Cruciferæ_, this order exhibits no endemic species, and four-fifths of the whole number are common plants of Central and Northern Europe. _Rubiaceæ_ and _Boragineæ_ have more representative species than is usual in mountain Floras; while there are but three species of _Rosaceæ_ in our list; and _Campanulaceæ_, _Primulaceæ_, _Coniferæ_, and _Cyperaceæ_ are each represented by a single species, and _Gentianeæ_ and _Junceæ_ are altogether absent from the higher zone.

Although statistical results, such as those given above, are not without interest, as throwing light upon the general characteristics of the Flora of a given region, any rational grounds for speculation as to the real affinities and past history of the vegetation must be derived from a closer examination of the individual species of which it is constituted. It is at least conceivable that two Floras should exhibit similar proportions of species belonging to the several natural groups, with no identical species, and with little or no indication of community of origin. The particulars given in our general list will have already led the reader to infer that the results of an examination into the distribution of the individual species that go to make up the Great Atlas exhibit some very peculiar features. Taking the totals at the foot of our list, and excluding cryptogams, it is seen that more than one-third of the species are plants of Middle and Northern Europe, while about one-sixth is made up of endemic species peculiar to Marocco, and, with few exceptions, not known out of the Great Atlas, more than half of the whole list belonging to one or other of these categories. The results, as shown in the following table, are still more remarkable when we separately examine the zones into which mountain vegetation is naturally divided. As in the former table the figures first entered in each column represent the number of species belonging to each category, those next given showing the percentage proportion borne by that number to the total proportion of each region.

TABLE II.—_Showing the distribution of the species of flowering
plants included in the Flora of the Great Atlas, and of the Sierra
Nevada of Granada,[2] and the Bulgardagh in Cilicia.[3]_

+-------------+------------+-------------+------------+------------+
| | | Wide-spread |Confined to | |
| |Mid-European|Mediterranean| adjoining | Endemic |
| | | | regions | |
+-------------+------------+-------------+------------+------------+
|Great Atlas, | 154 33·8| 165 36·2| 61 13·4| 75 16·6|
|including | | | | |
|all species | | | | |
|found above | | | | |
|1,200 m. | | | | |
|455 sp. | | | | |
| | | | | |
|Middle Zone | 106 31·1| 141 41·3| 46 13·5| 48 14·1|
|of Atlas, | | | | |
|from 1,200 | | | | |
|m. to 2,000 | | | | |
|m. 341 sp. | | | | |
| | | | | |
|Superior Zone| 78 44·3| 43 24·4| 20 11·4| 35 19·9|
|of Atlas, | | | | |
|from 2,000 m.| | | | |
|to 3,500 m. | | | | |
|176 sp. | | | | |
| | | | | |
|Superior Zone| 209 43·0| 74 15·2| 104 21·4| 99 20·4|
|of Sierra | | | | |
|Nevada, above| | | | |
|1,600 m. | | | | |
|486 sp. | | | | |
| | | | | |
|Bulgardagh | 159 18·0| 359 40·7| 157 17·8| 207 23·5|
|in Cilicia. | | | | |
|882 sp. | | | | |
+-------------+------------+-------------+------------+------------+

From this table we see that while over one-third of the whole Atlas Flora consists of plants of Central and Northern Europe, the proportion reaches nearly to one-half in the higher region (above 2,000 metres); and also that the proportion of endemic species, which in the aggregate is one-sixth of the whole, rises to one-fifth in the upper zone. On the other hand, the proportion of purely Mediterranean species, which amounts to 55 per cent. in the Flora of the middle zone, falls below 36 per cent. in the upper region. Of these Mediterranean species the large majority (more than two-thirds) are widely distributed plants, several of them extending to the mountains of Asia Minor, and twenty species only are exclusively confined to the Great Atlas and to the mountains of Southern Spain, the Lesser Atlas, or the Pyrenees. There is nothing in the distribution of these latter plants to indicate any special connection between the Atlas and any one of the mountain regions above mentioned. Six Atlas species are common to Southern Spain and the Algerian Atlas, six more are known only on the mountains of Southern Spain, five have been hitherto supposed to be peculiar to the Lesser Atlas, and three are elsewhere confined to the Pyrenees.

Some further light may be thrown on the origin of the Great Atlas Flora by considering the affinities of the plants which are reckoned in our list as endemic in Marocco, nearly all being confined, so far as we know, to the chain of the Great Atlas. Although all of these, along with some that we have classed as mere varieties, would be counted as distinct species by many botanists, a considerable number, amounting to more than a quarter of the whole, are, according to the views expressed elsewhere by the writer,[4] to be ranked as sub-species. But here again we fail to discover indications of special relations between the Great Atlas Flora and that of neighbouring mountain regions. Ranking as sub-species twenty-one out of the seventy-five endemic forms enumerated in our list, we find that ten of these are allied to widely spread Mediterranean species, three are related to plants of Central Europe, three to species common to Algeria and Southern Spain, three more to species confined to the Spanish peninsula, and two to endemic Algerian forms.

If we scrutinise in the same manner the endemic forms of the higher region of the Great Atlas, we find that out of the thirty-five enumerated eight, or less than one-fourth, are to be ranked as sub-species. Of these, three are nearly allied to wide-spread Mediterranean species, one to a plant common to Spain and Algeria, two to endemic Spanish species, one to an Algerian endemic form, and one is related to a species indigenous in the Alps and other high mountains of Central Europe.

While recognising the fact that the relations between the vegetable population of the Great Atlas and that of the south of Spain are less close than might have been expected on theoretical grounds, we must yet admit that, on the whole, the Great Atlas is more nearly connected in a botanical sense with this than with any other mountain region that is known to us; and it becomes a matter of some interest to compare closely the list of species obtained by us in the Atlas, with the comparatively well known Flora of Southern Spain. The results of this comparison are given for the Great Atlas generally, and for the superior zone separately, in the following table, in which the Atlas species are distinguished under five heads: 1, those found in the higher region of the Sierra Nevada; 2, in the mountain region of Andalusia; 3, in the lower warm region below the level of about 2,000 feet; 4, absent from Southern Spain, but found in the central or northern provinces; and 5, those not included in the Spanish Flora.

TABLE III.

[A: Superior region, Sierra Nevada B: Mountain region of Andalusia C: Lower region of Southern Spain D: Central, or Northern Spain, exclusively E: Absent from Spain]

+-------------------------------------------+----+----+----+----+----+ | | A | B | C | D | E | +-------------------------------------------+----+----+----+----+----+ |Great Atlas Valleys. 455 sp. | 103| 82| 100| 44| 126| |Superior region of the Great Atlas. 176 sp.| 61| 19| 20| 21| 55| |Great Atlas Valleys. 455 sp. | 103| 82| 100| 44| 126| |Superior region of the Great Atlas. 176 sp.| 61| 19| 20| 21| 55| +-------------------------------------------+----+----+----+----+----+

The figures given in this table are of much interest, proving, as they do, the wide differences that exist between the Floras of two mountain regions not widely separated from each other, and exposed to climatal conditions not altogether dissimilar. We see that three-sevenths of the plants found in the higher region of the Great Atlas are absent from the South of Spain, and that the same remark applies to considerably more than one-third of all the plants found in the portion of the Great Atlas visited by us, although a notable proportion (in both cases) is to be found in Central and Northern Spain. Especially noteworthy is the fact that many of the species thus absent in Southern Spain are plants of Central Europe, most of which extend to the northern part of the Spanish Peninsula, although some of them are altogether wanting in the Floras of Spain and Portugal.

A simple inspection of our list suffices to show that it discloses no trace of affinity between the Great Atlas Flora and that of the Canary Islands, or, to use a term of wider geographical import, that of Macaronesia. The few species belonging exclusively to the latter region and to Marocco are nearly all confined to the coast region.[5] Almost all the species common to the Atlas and to Macaronesia are widely spread Mediterranean plants that ascend from the low country into the valleys. The solitary mountain plant belonging to this category is _Arabis albida_, the southern form of _A. alpina_, common in the East, and in the Apennines of Central and Southern Italy, but which, strange to say, has not been found in Spain. In Teneriffe, as in the Atlas, it ascends to about the level of 2,700 metres above the sea. The only fact suggesting a remote affinity between the Great Atlas and Macaronesian Floras is the presence in the former of a species of _Monanthes_, a generic group hitherto found only in the Canary and Cape de Verde Islands. But the absence of any closer connection clearly shows that the separation between the Macaronesian group and the main land of Africa must date from a period, even geologically speaking, remote.

When we come to sum up the results of the foregoing discussion, bearing always in mind the fact that we possess a mere fragment of the Flora of the Great Atlas, and that future exploration may largely modify our conclusions, we find as its most striking characteristic the presence of a large proportion of plants of Central and Northern Europe, along with a considerable number of peculiar species not hitherto known elsewhere; and we observe that these two constituents, which together form about one-half of the Flora of the region here discussed, amount to very nearly two-thirds of the species found in the higher zone. We remark that of these northern plants none are of Alpine or Arctic type, that nearly all belong to what has been called the Germanic Flora, and all are plants of the plain, not in Europe characteristic of mountain vegetation.[6]

Of the species belonging to the Mediterranean region, which constitute more than one-half of the vegetation of the middle zone, and about one-third of that of the higher zone of the Atlas, the large majority are widely diffused species. The remaining number, for the most part mountain plants, may be divided into three nearly equal sections, some being common both to Southern Spain and Algeria, others to the Atlas and Southern Spain exclusively, and others to the Great Atlas and the Lesser Atlas of Algeria. Nothing indicates any special connection with the Floras of either of those regions.

The absence of any distinct generic types from the Great Atlas Flora has already been remarked. It is not less important to note the absence of any of the southern types, characteristic of the sub-tropical zone, some representatives of which are found in the same or even in higher latitudes, in Arabia, Syria, Persia, and Northern India, and which also appear in the Canary Islands. We finally are led to regard the mountain Flora of Marocco as a southern extension of the European temperate Flora, with little or no admixture of extraneous elements, but so long isolated from the neighbouring regions, that a considerable number of new specific types have here been developed. The physical causes which have operated to bring about these conditions are doubtless numerous and complicated, but the most important of them are easily indicated. The influence of the Atlantic climate, and the prevailing direction of the aërial and oceanic currents, have fitted this region for the habitation of such northern species as do not require a long period of winter repose. In the present condition of the African continent, the Great Desert, extending for a distance of 700 or 800 miles between the Atlas and the river region of tropical Africa, effectually prevents the northward extension of most forms of animal and vegetable life; while in a period geologically recent, it is most probable that the same area was occupied by a wide gulf, which served the same purpose of barring the migration of southern forms.

It may be premature to attempt to trace in further detail the origin of the Great Atlas Flora; but the facts already ascertained certainly authorise some negative inferences. The absence of plants of Arctic type proves that if some mountains of Southern Europe received contributions to their vegetation during the glacial period by means of floating ice-rafts, that mode of diffusion did not extend to the Great Atlas. If we suppose that during the glacial period the temperature of the region north of the Atlas had fallen so low as to permit the migration of northern species across the intervening low country, we find it difficult to understand why so many species which, according to this theory, must have retreated to the Atlas on the subsequent rise of temperature, should have failed also to find a refuge in the mountains of Southern Spain.

It is a further difficulty that if the constituents of the Great Atlas Flora had, to a large extent, travelled by the route here indicated, other species, now inhabiting the mountains of Southern Spain, could scarcely fail to take the same road, and a much nearer connection than is now apparent would have been established between the Floras of these two mountain regions.

It is, at least, possible that the wide diffusion of many of the species constituting the so-called Germanic Flora may date from a period much more remote than is ordinarily supposed; and it is a circumstance not without significance that so many species of this type prove themselves capable of tolerating wide variations in conditions of soil and climate.

FOOTNOTES:

[Footnote 1: In the Superior Zone of the Sierra Nevada I include all species found above the level of about 1,600 m., considering this to correspond with the level of 2,000 m. in the Great Atlas.]

[Footnote 2: The name Sierra Nevada is here used in a wide sense, and is intended to include the Serrania de Ronda, and the other mountains of Andalusia. Under this head, the plants classed as ‘confined to adjoining regions’ are either common to the Sierra Nevada and the mountains of Northern Spain, including the Pyrenees, both Spanish and French, or else are common to the Sierra Nevada and the mountains of Northern Africa.]

[Footnote 3: The Bulgardagh has been introduced into this table rather for the sake of contrast than as showing similarity to the conditions in the Great Atlas. The species classed as ‘confined to adjoining regions’ are all found in the other mountain districts of Asia Minor, and it has been necessary to include under the heading ‘Wide-spread Mediterranean’ a large number of Oriental species, whose western limit is in Greece or Crete. As compared with the Great Atlas, the number of species common to the western and south-western parts of Europe is here quite insignificant.]

[Footnote 4: See ‘Spicilegium Floræ Maroccanæ,’ in _Proceedings of the Linnæan Society_, ‘Botany,’ vol. xvi. parts 93 to 97 inclusive.]

[Footnote 5: The only possible exception to this statement among the plants enumerated in our list is that entered as _Asparagus scoparius_, Lowe (?) From the differences between the foliage and that of other known species it was at first entered as a new species peculiar to the Atlas. Subsequent comparison with a Madeira specimen from the late Mr. Lowe suggested their possible identity. Should this be hereafter verified, the number of endemic species in the tables given above must be reduced from 75 to 74.]

[Footnote 6: The only apparent exception is _Sagina Linnæi_. This is habitually a mountain plant; but in Germany it is often seen in the moorland region, at a level of about 2,500 feet above the sea.]

* * * * *