240 STUDIES IN SEEDS AND FRUITS 



seed remains always in the same hygrometric state, and retains the 

 same average weight, showing only fluctuations of x or 2 per cent, on 

 either side of a constant mean (p. 226). 



(3) As regards the impermeable seed, it is urged that as long as it 

 preserves its weight and is non-hygroscopic, we may assume that it 

 retains its germinative powers (p. 226). 



(4) The constancy of the weight of impermeable seeds during a 

 period of three or four years is then illustrated in a tabular form 

 (p. 228). 



(5) The failures in impermeable seeds are at once detected by the 

 balance. They are instructive in their presentation of permeabiUty as 

 a quahty by default, the impermeable seed owing to some defect in its 

 coats gradually gaining weight and slowly assuming the rdle of a 

 permeable seed (p. 229). 



(6) Reference is made at some length to the very different view of 

 the ultimate fate of the impermeable seed held by rrofessor Ewart. 

 In the case of Acacia seeds he considers that in the course of years 

 they become as dry as corresponding inorganic material, and may hold 

 less than i per cent, of moisture. This view is controverted, and an 

 explanation of its origin is suggested (p. 230). 



(7) It is shown that in all experiments on the weight of permeable 

 seeds extending over some time, the disturbing effect of the hygroscopic 

 reaction, involving as it does a variation of 2 or 3 per cent, of the total 

 weight, presents a great obstacle to the detection of small differences. 

 For this reason, therefore, the experiments should cover many years 



(P- 235)- 



(8) It is considered that the increase in weight of i to 2 per cent. 



recorded by Van Tieghem and Bonnier, in the case of seeds of peas, 

 haricots, vetches, etc., after a two years' experiment, comes within the 

 ordinary hygroscopic range and does not necessarily imply an increase 

 in the average weight (p. 236). 



(9) With the object of testing the influence of time on seed-weight, 

 the author began four years ago a series of experiments on the seeds of 

 nearly thirty genera, the intention being to continue them for many 

 years (p. 237). 



(10) The necessity in weighing experiments extending over long 

 periods of first selecting seeds that have completed the drying process 

 is pointed out (p. 237). 



(11) In this connection it is shown that whilst some seeds, as those 

 of leguminous pods and of similar dehiscent fruits, are almost completely 

 air-dry when liberated naturally from the fruit, others from fleshy or 

 watery 1 fruits have still 40 or 50 per cent, of their weight to give up to 

 the air. Seed-like fruits, as grains of cereals and acorns, have to submit 

 to a "sweating" or "airing" process before storage (p. 238). 



