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