Chapter I: Part I: Pollination Studies of Seed Production

Unsatisfactory yields of sweet-clover seed 1
Previous investigations of the pollination of sweet clover 2
Outline of pollinating experiments 3
Structure of the flowers of Melilotus alba 4
Development of the floral organs of sweet clover 5
Fertilization in Melilotus alba 8
Development of the seed 8
Mature pollen of sweet clover 9
Germination of the pollen 9
Cross-pollination and self-pollination of sweet clover 10
Artificial manipulation of sweet-clover flowers 10
Seed production of Melilotus alba under ordinary field
conditions 13
Efficiency of certain kinds of insects as pollinators of
sweet clover 14
Relation of the position of the flowers on Melilotus alba
plants to seed production 19
Influence of the weather at blossoming time upon seed
production 20
Insect pollinators of sweet clover 21
Effect of moisture upon the production of Melilotus alba seed 22

Part II.--Structure and Chemical Nature of the Seed Coat
and its Relation to Impermeable Seeds of Sweet Clover.
Historical summary 26
Material and methods 30
Structure of the seed coat 31
Microchemistry of the seed coat 33
The seed coat in relation to the absorption of water 34
A comparison of permeable and impermeable seed coats 34
The action of sulphuric acid on the coats of impermeable seeds 35

Literature Cited 36

WASHINGTON GOVERNMENT PRINTING OFFICE

1920

UNITED STATES DEPARTMENT OF AGRICULTURE

BULLETIN No. 844

Contribution from the Bureau of Plant Industry

WM. A. TAYLOR, Chief

Washington, D. C. PROFESSIONAL PAPER August 11, 1920

SWEET-CLOVER SEED

Part I.--Pollination Studies of Seed Production

Part II.--Structure and Chemical Nature of the Seed Coat and its Relation to Impermeable Seeds of Sweet Clover

By H. S. Coe, _formerly Assistant Agronomist, Office of Forage-Crop Investigations_, and J. N. Martin, _Professor of Morphology and Cytology, Iowa State College_.

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