THE REST-PERIOD OF SEEDS 431 



In different years, when the season is unusually mild, all 

 the stages above referred to the month of May will be found 

 in April. The seeds will not generally be found all germinat- 

 ing in the same berry, but all will show embryos advanced 

 in growth. Nature only offers a small number of fruits to 

 illustrate the germination of the seeds on the plant, since the 

 final stage is usually anticipated by the early shrivelling and 

 detachment of the berry when the embryo is 3 or 4 millimetres 

 long, the result of late frosts, wind, and rain. However, of 

 the surviving berries the proportion with germinating seeds 

 in May will vary from 10 to 50 per cent. By the beginning 

 of June all the fruits have fallen. I have here been describing 

 the behaviour of Ivy berries in the mild climate of South 

 Devon. The growth of the embryo in the spring is a 

 good deal influenced by the situation of the plant. Thus in 

 sunny places sheltered from the cold winds it will be much 

 in advance of that found in plants growing in bleak, exposed 

 localities. 



The nature of the growth of the embryo of the Ivy during TWO modes 

 the winter is well brought out in the table. The seed grows the^emliryo 01 



with the berry and the embryo grows with the seed, the , f the l jy m 

 i i 11 i 1-1 the seed on 



increase in its proportional bulk being but slight. There is the plant. 



little or no growth at the expense of the endosperm, the 

 embryo remaining white and the cotyledons retaining their 

 small dimensions. But with spring in progress the berry and 

 the seed no longer add to their size. The embryo, now 4 

 or 5 millimetres long, grows independently. Its cotyledons 

 enlarge and its whole surface becomes green, this independent 

 growth being associated with a gradual diminution of the 

 food-reserve, so that when the seed is found germinating in 

 the berry on the plant, the albumen has mostly disappeared. 

 The two kinds of growth of the embryo, first during the 

 winter with the seed and the fruit, and then in the spring at 

 the expense of the albumen, are the conspicuous features in 

 the vivipary of the seeds of the Ivy. We can thus distinguish 

 two stages in the after-ripening of these seeds. 



