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

CONTENTS

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

UNITED STATES DEPARTMENT OF AGRICULTURE

BULLETIN No. 844

Contribution from the Bureau of Plant Industry
WM. A. TAYLOR, Chief

Washington, D. C.PROFESSIONAL PAPERAugust 11, 1920