466 STUDIES IN SEEDS AND FRUITS 



my estimates come close to that of HofFmann, the estimate of Nobbe 

 is considerably greater, being in excess even of the ordinary weight of 

 a saturated seed, an increase of 120 per cent, being required for 

 saturation (see p. 44). Nobbe took as the iirst indication of germina- 

 tion the protrusion of the tip of the radicle through the coats ; but it is 

 shown in the next paragraph that in the case of Peas, when the coats 

 are much wrinkled, excessive estimates of the swelling capacity may 

 thus be formed. 



Two varieties of Peas were used by me — the Early Sunrise Pea (a), 

 a slightly wrinkled kind, and a Marrowfat Pea (b), with excessively 

 wrinkled coats. The causes of the great difference in the swelling 

 capacities of these two varieties, 9 1 per cent, for the slightly wrinkled 

 and 137 per cent, for the greatly wrinkled seeds, lie in the excessive 

 wrinkUng of the coats, which not only allows an excess of water to 

 collect between the kernel and its loosely fitting coats, but also permits 

 a considerable growth of the radicle before the irregular rupture of the 

 coats, so that when the seed is weighed it is well advanced in germina- 

 tion and in a saturated state. This therefore explains not only my 

 excessive result for Marrowfat Peas, but probably also Nobbe's abnormal 

 estimate for Faba vulgaris. 



NOTE 2, A (p. 30). 



Comparison of the weight of a leguminous seed dried under ordinary air- 

 conditions after swelling for germination with its original weight in the 

 resting state. 



There are several disturbing causes that would come into play in 

 •drying a seed that has swelled for germination. In my own experi- 

 ments only those seeds were accepted which had proved their 

 germinative capacity by displaying evident signs of the earliest stage i 

 of the process. Owing to the slight growth of the radicle thus 

 involved, this would slightly increase the weight of the dried seed.| 

 However, on comparing the weight of seeds just before and just after 

 the first signs of germination, I find that the correction to be applied 

 rarely exceeds 0*5 per cent. 



This increase, however, would be counterbalanced by the slight 

 decrease in weight during the swelling process arising from the loss of 

 solid materials which pass into the water that dampens the surface of 

 the swollen seed. This is evident enough when seeds are allowed to 

 go through the whole swelling stage immersed in water, especially with 

 highly coloured seeds, when the water is deeply stained, or where 

 colloidal substances in the coats ooze out as mucus or slime. Easily 



