VITALITY AND GERMINATION OF SEEDS. 219 



minated seeds. The vitality of the majority of the Peas 

 is destroyed by the alternate soaking and drying in water 

 without any germination, as indicated by the elongation 

 of the radicle and the splitting of the integuments, having 

 taken place. 



One effect of the successive soaking and drying is to 

 render the integuments of the Peas extremely permeable 

 to water. The coats of Peas dried after the 2nd or 3rd 

 soaking begin to wrinkle immediately they are placed in 

 water whilst in two or three minutes the integuments are 

 tightly distended by the water, which passes through 

 them with much greater rapidity than it is absorbed by the 

 cotyledons. The extreme rapidity with which the water 

 penetrates may be partly due to the formation of 

 osmotically active substances in the seed when previously 

 soaked, but is also due to an enlargement of the inter- 

 molecular spaces of the integument caused by the previous 

 forcible passage of water through them. 



In certain cases it was found that in these and in other 

 experiments where the vitality of both radicle and plumule 

 had been destroyed, that the cotyledons were three or 

 four weeks after planting still alive, and green, and that a 

 portion of their starchy contents had been fermented. 

 The vitality of the cotyledon is therefore independent of 

 that of either radicle or plumule. In all such cases, 

 however, the cotyledons eventually perish having used 

 but little of the contained food material. 



In normal Peas it is often found that as many as five 

 per cent, of the seeds on germinating form a radicle only, 

 and on separating the cotyledons and examining the 

 plumule the latter is seen to be decayed and was evidently 

 dead when the seed was planted. In such cases the 

 radicle may grow to a considerable length, six inches or 

 even a foot, but the plant, if so incomplete a specimen 



