770 



Journal of Agricultural Research 



Vol. VI, No. 20 



Table IV. — Rate at which impermeable seeds became permeable when stored in manila 



envelopes 



a This lot of hairy-vetch seed was grown by the Office of Foreign Seed and Plant Introduction, Bureau of 

 Plant Industry, at Chico, Cal. 



3. Impermeable alfalfa and hairy-vetch seed * became permeable more 

 rapidly than impermeable clover seed, 82 per cent of one lot of hairy- 

 vetch seed becoming permeable in one year. 



Besides the kinds of seed given in Table IV, five lots of okra seed 

 gathered in 191 1 were tested when fresh and six months, two years, 

 and three years later. When fresh, all seeds softened and an average 

 of 98 per cent germinated. Six months later only 23 per cent germinated 

 and 71 per cent were impermeable. During the following two and one- 

 half years very little change in permeability occurred. 



It should be added that there was a slight decrease in the viability of 

 the red-clover seed during the third and fourth years, and a large de- 

 crease in the viability of the vetch seed during the fourth year. 



VARIATION IN THE RATE AT WHICH IMPERMEABLE SEEDS OF A SINGLE 

 SPECIES BECOME PERMEABLE 



The impermeable seeds in some of the lots included in Table IV 

 became permeable in dry storage much more rapidly than those of 

 other lots of the same kinds of plants. In fact, the percentage of the 

 impermeable seeds in different lots of red-clover seed which became 

 permeable in four years varied from about 15 to about 80. This varia- 

 tion is further emphasized by the results of tests conducted in the fall 

 and winter of 1 914-15 and in September and December, 191 5, using 



1 The vetch seeds in the lots here considered were thoroughly dry and black when first tested. Vetch 

 seed, while it remains green in color and has a high water content, contains but a small percentage of im- 

 permeable seed or none. This percentage increases in storage for a time before any decrease takes place. 



