THE SHRINKING AND SWELLING SEED 209 



taken by the coats and the kernel in the process. We have, 

 in fact, the " swelling " data for the coats and the kernel in 

 forty-four species, of which all but ten are leguminous, the 

 residue belonging to a variety of orders, such as Convolvulaceae, 

 Euphorbiaceae, Iridaceas, etc. 



Many influences come into play in determining the swelling The dis- 

 ratios of the coats and of the kernel of the resting seed pre- influeiKes. 

 paring for germination, influences that are more numerous, 

 however, with the seed's coverings than with its kernel. In 

 the case of the kernel there is the relative dryness of that of 

 the impermeable seed as compared with that of the permeable 

 seed, and there is the peculiar regime of the oily seed, as in 

 Rkinus, where the oil seems to take a vicarious part, much less 

 water than usual being required for germination. In the case 

 of the coats there is also the relative dryness of the seed- 

 coverings in typical impermeable seeds ; but this influence is 

 at times masked in the swelling process of seeds like those of 

 Mucuna and Dioclea, where the kernel may begin to germinate 

 whilst its coats are still partly dry. Then we have the diverse 

 influence of the various textures of the coverings themselves, 

 influences that are far more diverse than any that could be 

 off^ered by the kernel, however much it may vary in consistence, 

 as indicated by such terms as farinaceous, fleshy, horny, oily, etc. 



If we begin by comparing the swelling ratios of coats and The swelling 

 kernel for all the plants named in the following table, we find kernel is 

 that in just about two-thirds the kernel has the largest ratio. "^r"^gj.^than 

 But if we except the fact that all the four species of Canavalia that of the 

 and both the species of Iris are included in the smaller group 

 where the coats have the largest ratio, there is little that is 

 determinate in such an arrangement, species of the same 

 genera being sometimes separated, as in the cases of Cassia and 

 Erythrina^ whilst permeable and variable seeds are more or 

 less divided between the two groups, the larger group being 

 made up of the three types of seeds, impermeable, permeable, 

 and variable. It is not therefore from such an arrangement 

 that we should expect to be able to frame any definite infer- 



14 



coats. 



