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, 

 lernelso? these seeds exhibit the extreme behaviour of the perme- 

 'arUble ^ble and impermeable seeds, in the first case merely the 

 .bsorbing ordinary hygroscopic variation of i or 1-5 per cent, on 

 he 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. 



