128 STUDIES IN SEEDS AND FRUITS 



impermeability in water before testing the amount of its water- 

 contents, and this difficulty is very apt to arise in dealing with 

 variable seeds, notably in the seeds of Poinciana regia^ which 

 behave almost like permeable seeds. 



It is to seeds like those of C^salpinia Sappan and Entada 

 polystachya, where we can with some confidence distinguish the 

 two types of seeds by their external characters before the 

 experiment, that we must appeal. In their case it is plainly 

 shown in the table that the seeds which imbibe in the broken 

 condition most water from the air are those which lose least 

 water in the oven, or, in other words, that the ultra-dryness of 

 impermeable leguminous seeds is simply a diminution in the 

 water-contents as compared with permeable seeds. Thus we 

 find for Casalp'tnta Sappan that when the seeds held about 14 

 per cent, of water they did not increase their weight when ex- 

 posed in a broken state to the air. On the other hand, when 

 their water-contents amounted to less than 10 per cent, they 

 increased their weight about 9 per cent, by abstracting water 

 from the air. Similar results were obtained for Entada 

 polystachya. Thus : 



(Seeds with 14 per cent, of water merely behave hygro- 

 scopically when broken. 

 Seeds with 9-7 per cent, of water add 9 per cent, to their 

 weight when broken. 



(Seeds with 10 per cent, of water add i'6 per cent, to their 

 weight when broken. 

 Seeds with 6 per cent, of water add 9*4 per cent, to their 

 weight when broken. 



The data given in the table for permeable seeds of other 

 than leguminous plants are interesting, as they illustrate the 

 fact that many permeable seeds may hold as little water as some 

 of the impermeable leguminous seeds. This is particularly 

 clear when we distinguish between the coats and the kernel, 

 as is done in the table. Here we find that the kernels of 

 permeable seeds like those of Citrus^ Hura, etc., may hold less 

 than 9 per cent, of water. Doubtless the presence of oil goes 



