484 



STUDIES IN SEEDS AND FRUITS 



retain a greenish hue and are thickish in appearance. In the second 

 case they are pale and parchment-like and relatively thinner. 



This is associated with different behaviours in the balance, the first 

 type show^ing in average pods a pericarp-proportion of over 40 per cent, 

 of the total weight, the second type, on the other hand, a pericarp-propor- 

 tion of only 20 per cent. The same indication is also afforded by the 

 difference in the actual weights of the dried fruit-cases, those of the 

 pods that dried after detachment averaging 15 or 16 grains, and those 

 of the pods dried on the plant only from 7 to 9 grains. 



By experiments we can determine that the pericarp or fruit-case of 

 the detached fresh pod loses about 86 per cent, of its weight when 

 dried ; whilst if we know the shrinking ratio of the entire pod and the 

 average proportion of parts in the fresh fruit and in the fruit dried on 

 the plant, we can easily show that the pericarp then loses in drying 

 about 93 per cent, of its weight. Thus, taking the shrinking ratio of 

 the ripe moist fruit at 100 to 20 (involving a loss of 80 per cent.) and 

 the pericarp-proportions of the moist and dry pods at 60 and 20 per 

 cent, respectively, we obtain the following results for a typical six- or 

 seven-seeded fruit : — 



The Shrinking of Parts of a Ripe Six- or Seven-Seeded Pod 

 of pisum sativum when dried on the plant. 



The shrinking ratio can be obtained by comparing the average weights in the moist 

 and dry condition of a large number of pods from the same plant and containing the 

 same number of seeds. 



The difi:erences in the behaviour of the pods, whether dried in the 

 detached condition or allowed to dry on the plant, may shortly be 

 summed up from the previous remarks in the following manner : — 



