THE REST-PERIOD OF SEEDS 435 



eleven out of fifty-five nuts were found in the typical 

 germinating state about seventeen days after. The fruits 

 had germinated whilst actually drying ; and I estimated their 

 loss of weight when germination began at from 10 to 20 

 per cent., the total loss of weight of a mature fruit when 

 completely air-dried being from 50 to 60 per cent. The 

 same thing happened under the same circumstances in the 

 two following Octobers. In an experiment carried out whilst 

 writing this chapter, I placed thirteen ripe acorns in a dry cup. 

 In nine days one was protruding its radicle and two were 

 splitting their shells, the aggregate loss of weight since the 

 seeds were gathered in the moist entire condition from the 

 tree being just 10 per cent. 



We are not concerned here with after-ripening, such as 

 frequently occurs with detached albuminous seeds, since in 

 the mature acorn on the tree the embryo is fully formed 

 and develops a plumule which may be turning green. The 

 interest lies in the fact that germination took place in the 

 case of a mature exalbuminous seed in a drying fruit. It 

 is evident that with the acorn the ripe moist seed is not 

 necessarily prevented from proceeding continuously with its 

 growth by drying in air for a week or two. But the drying 

 process must be slow. In most cases the loss of water is too 

 rapid and the tendency to proceed at once to germinate is 

 suppressed. Evidently the detached ripe acorn, provided that 

 the drying is checked, can make good use of the water it 

 holds, which is more than is actually needed for the continued 

 growth and germination of its seed. Anything that impedes 

 the air-drying process of the freshly detached acorn will assist 

 the seed in its endeavour to dispense with the rest-period 

 altogether. 



In this way we may explain Uloth's observation of acorns 

 germinating in ice. The explanation given in Nobbe's book Uloth's 

 (p. 104) is, that the requisite water would be supplied by the f acorns n 



melting of the surrounding ice through the natural warmth germinating 



in ice. 

 of the seed. However, we learn from my observations above 



