i6o 



STUDIES IN SEEDS AND FRUITS 



of seeds the proportion of permeable seeds was probably very- 

 small, that is to say, under lo per cent.; and doubtless the 

 change of weight was experienced by a very few seeds. The 

 rise in weight of the three permeable kinds of seeds in Jamaica 

 and the fall after returning to England are characteristic ; but 

 the difference between them is probably due to the varying 

 hygrometric conditions of the air when the two sets of obser- 

 vations in England were made. On the whole, however, it may 

 be considered that the changes in weight experienced by these 

 permeable seeds between warm and cool latitudes are within 

 the limits of the hygroscopic range defined a few pages back. 



In all experiments for determining the limits of hygroscopic 

 variation it is requisite that the seeds should have completed 

 the drying process and that they should be, as far as their 

 water-contents are concerned, in a state of equilibrium with 

 the air. The method at first employed in investigating the 

 hygroscopic behaviour of seeds was, as already indicated, to 

 weigh them daily for ten or fourteen days when the weather was 

 changeable. The variation was then stated as a percentage of 

 the total weight of the seed, and this was termed the " hygro- 

 scopic range." In such experiments four or five kinds of seeds, 

 of both the permeable and impermeable types, were experi- 

 mented on at the same time. The results of one of these 

 experiments in Jamaica are given below in the form of a 

 diagram ; and in order to obtain a more graphic effect, they 

 have all been computed for looo grains of each kind of seed, 

 whilst the prevailing weather conditions as regards rain have 

 been roughly indicated by black and white squares. The 

 following seeds were employed : — 



112 seeds of Anona palustris, weighing 



74 „ Anona muricata (Sour Sop), „ 



85 „ Citrus decumana (Shaddock), „ 



212 „ Adenanthera pavonina „ 



3 „ Entada scandens „ 



The first three are permeable seeds, the ranges for the two 

 species of Anona being 1-3 and \"i per cent., whilst that for 



