THE REST-PERIOD OF SEEDS 439 



the first word to say in shifting the plane of the rest-period. But re- 

 stricting his remarks to the special influences of the fruit, the author 

 points out that the more the fruit's growth is in advance of that of the 

 embryo, the earlier should be the onset of the rest-period, and that only 

 when the two are co-ordinated does true vivipary occur (p. 425). 



(13) Then follow the results of the writer's observations on the 

 viviparous tendency displayed by the seeds of the Ivy [Hedera Helix), 

 and of the Oak [Quercus Robur). In the case of the Ivy it was 

 ascertained that the ripening of the seed on the plant during the 

 winter is followed by germination in the spring without the inter- 

 vention of a rest-period of any long duration. The ripening in the 

 winter months is characterised by the associated growth of berry, seed, 

 and embryo, the embryo growing as the endosperm increases. The 

 ripening in the spring is confined only to the embryo, which grows at 

 the expense of the endosperm. The result is germination on the 

 plant in the case of the seeds of berries that remain long attached to 

 the parent (p. 427). 



(14) In the case of the Oak it is established not only that the 

 freshly detached moist acorns can be readily induced to pass on to 

 o-ermination, but that there is a decided tendency for the ripe acorn on 

 the tree to dispense with the rest-period. This viviparous habit has 

 been already regarded as the final expression of the tendency of a seed 

 to continue its growth on the plant after the fruit-case has commenced 

 to dry, a capacity that was established for the seed of the acorn in 

 Chapter XIV. As a result the seed not infrequently becomes too 

 large for the fruit-case and splits the shell, the radicle protruding when 

 the" acorn remains some time longer on the tree. The proportion 

 of acorns beginning to germinate on the tree varied between 2 and 

 10 per cent. (p. 432). 



(15) The chapter is concluded with some notes on the germination 

 of the seeds of Artocarpus incisa (seeded variety of the Bread-fruit tree) 

 in the fruit on the tree, and on the continuous growth of the embryo 

 of Crinum during the drying of the seed (p. 436). 



