  | Page | 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
BULLETIN No. 844 Contribution from the Bureau of Plant Industry
WM. A. TAYLOR, Chief | | | Washington, D. C. | PROFESSIONAL PAPER | August 11, 1920 |
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