122 STUDIES IN SEEDS AND FRUITS 



the air ; and if the excess weight, due to the absorption of 



aqueous vapour by the ultra-dry kernel, is only 3 or 4 per 



cent., it is difficult to exclude the disturbing influence of the 



hygroscopic reaction. Such experiments in the tropics are 



likely to be terminated by attacks of mould, and even in 



England it is necessary that they should be carried out in a 



dry room. The appearance of mould is usually preceded 



by a marked increase in weight. The bared kernels of an 



inland Jamaican species of Guilandina gained about 6 per cent. 



in weight during the first ten days, and, subject to slight 



variation, preserved this excess for about two months, when 



very damp weather followed, and the seeds, after having 



augmented their weight to 10 per cent., were attacked by 



mould. 



With regard to the " variable " group of seeds, where 



both permeable and impermeable seeds occur in the same 



plant, only a few remarks will be needed before giving the 



tabulated results of my observations. As concerning the 



The capacity bared kernel's capacity for absorbing water from the air, 



kernelso?'^ these seeds exhibit the extreme behaviour of the perme- 



variable ^JqXq and impermeable seeds, in the first case merely the 



seeds of . ^ . . . . 



absorbing ordinary hygroscopic variation or i or i'5 per cent, on 



the air. '^°'" either side of the mean, in the second case a marked and 

 permanent increase often of 10 per cent, or more. If 

 we had to handle two samples of seeds from the same 

 plant which presented this great contrast in behaviour, we 

 should at once know that one sample consisted only of 

 permeable seeds and the other sample only of impermeable 

 seeds. Almost always, however, the sample would be mixed, 

 and then we should get an intermediate result, for instance, 

 an average increase of weight, after allowing for the hygro- 

 scopic reaction, of 4 or 5 per cent. Some seedsman, more 

 practical than the author, might be able to make a scale of 

 comparison which could be used for proving his seeds ; but 

 it would be requisite to have a standard of comparison for 

 each species. 



