766 Journal of Agricultural Research vol. vi. No. *o 



in commercial lots of seed of the same plants. There was but little 

 difference in this respect between the impermeable seeds of hand-gathered 

 lots and commercial lots of the other species of plants. 



Almost all of the seeds of each kind of plant which softened at any time 

 during the three years germinated and produced vigorous seedlings. 



Besides seeds of the species given in Table II a few impermeable seeds 

 of kidney bean, garden pea, and cowpea were included in the tests. All 

 of the beans and peas softened and germinated within three months, 

 and all of the cowpeas within eight months. 



INFLUENCE OF MATURITY ON THE RATE OF SOFTENING OF IMPERMEABLE 

 RED-CLOVER AND ALSIKE-CLOVER SEEDS IN WET BLOTTERS 



The lots of hand-gathered seed included under Table III were 

 thoroughly mature and dry in the heads before being removed from the 

 plants. Figure I shows graphically the comparative rates of softening 

 of such well-matured impermeable red-clover seed and of impermeable 

 red-clover seed of two other degrees of maturity. 



Seven of the eight lots of slightly immature seed were gathered at the 

 same time and from the same cultivated rows of plants as were seven 

 of the eight lots of mature seed, the former being taken from heads 

 which were slightly green and succulent, the latter from black, dry heads. 

 The three lots of light, immature seed used in the comparison were sepa- 

 rated from three of the lots of slightly immature seed by a gravity blowing 

 machine. Only seeds of good appearance, though frequently of small 

 size in the immature lots, were used in the tests. 



The average percentages of the mature seeds, the slightly immature 

 seeds, and the more immature seeds which remained impermeable after 

 10 days in wet blotters and from which the rates of softening were 

 calculated were respectively 84, 72, and 27. 



Of the impermeable seeds from lots of light, immature seed, 78 per 

 cent softened in one month and 100 per cent in 13 months. In contrast 

 to this, only 5 per cent of the impermeable seeds from lots of well-matured 

 seed softened in one month and 44 per cent of them remained imperme- 

 able after three years. 



The differences in the rate of softening of impermeable seeds from 

 lots of mature and immature seeds of alsike clover were similar to those 

 shown for red-clover seed. No other species of plants were investigated 

 for rate of softening. 



Hiltner (11) has shown that the percentage of impermeable seeds and 

 the rate at which they soften when placed under conditions favorable to 

 imbibition may in some cases be greatly altered by previous drying. 

 Although only seeds which seemed to be thoroughly dry were used in these 

 experiments, it is possible that artificial desiccation of the less mature 

 lots would have increased the percentages of impermeable seeds and de- 



