Note 4 — Part II.—STRUCTURE AND CHEMICAL NATURE OF THE SEED COAT AND ITS RELATION TO IMPERMEABLE SEEDS OF SWEET CLOVER.[3]

The term "permeable" is used in this paper to designate seeds whose coats are permeable to water in two weeks or less at temperatures favorable for germination, while the term "impermeable" is used to designate seeds whose seed coats are impermeable to water for this length of time when temperatures are favorable for germination. Impermeable seeds are commonly referred to as "hard seeds," and they may become permeable in time.