228 



STUDIES IN SEEDS AND FRUITS 



THE WEIGHTS OF IMPERMEABLE SEEDS DURING PERIODS OF 

 FROM TWO TO FOUR YEARS. 



The aberrant 

 behaviour of 

 an imperme- 

 able seed is 

 at once de- 

 tected by 

 the balance. 



Note. The observations were made at irregular intervals every few months. The 

 first three seeds of Entada scandens were carried to Jamaica and kept there some months 

 during the first year, which accounts for their rather larger variation of 0*2 grain ; but 

 in the last three years in England the weighings only varied 0*1 grain. A pebble of 

 quartz would probably have behaved in the same way ; and evidently the cause of the 

 variation is largely instrumental. This is also true of Guilandina bonducella. The 

 samples of the seeds of Adenanthera pavonina and Ipomcea pes-capm were small in 

 weight ; but the results give the same general indications. In connection with the last- 

 named it is shown on page 169 that its pubescent hairs have a very slight disturbing 

 effect. 



However, although this is the rule, cases of failure are not 

 infrequent, and their aberrant behaviour is at once detected by 

 the balance. Some slight defect in the coats, due probably 

 to some imperfection in the shrinking process, gives time 

 its opportunity ; and the seed within, brought into relation 

 with its surroundings, responds to the changing atmospheric 

 conditions, first slowly and then more rapidly, until it assumes 

 the r61e and the limited life-duration of a permeable hygro- 

 scopic seed. The manner in which this change of state is 

 carried out has been described in Chapters IV. and VI. in 

 connection with the results of puncturing or filing the seed- 

 coverings. The seed gradually gains weight in the course of 

 months, taking up from the air the water which it previously 

 lacked ; and, as is shown in the case of filed seeds of Guilandina 

 bonducella^ it may retain its germinative capacity for two years 

 after it has virtually lost the protection of its coats, an event, 



