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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 |
