4 ON SEEDLINGS 



to ask why they were formed as they are, and why they 

 differed so much. So they grew, and beyond that it did not 

 occur to me, nor I think to most, that it was possible to in- 

 quire. 



I now propose, however, to suggest reasons which may 

 account for some, at any rate, of these differences. 



In previous memoirs I have discussed the causes which 

 regulate the forms of seeds, and will not now therefore enter 

 into them. I may, however, observe that the shape of 

 the cotyledons seems to have little, if any, influence on that 

 of the seed. 



OVULE AND SEED. 



The seed of a flowering-plant contains a more or less 

 highly developed embryo, which, after a certain time, will, 

 under favourable conditions, resume growth, emerging from 

 the seed-coat to produce the young plant or seedling. In the 

 section of flowering-plants known as Gymnosperms, and 

 including the Conifers and Cycads, the seeds are borne naked 

 on an open scale, while in the far larger section of the Angio- 

 sperms they are protected till ready for dispersion in the 

 closed cavity of the Fruit. 



The seed is the result of the fertilisation of the ovule by 

 the pollen. The effect of fertilisation, however, extends 

 beyond the ovules to the ovary in which they are contained, 

 causing often immense increase in size, as well as important 

 structural changes. The ovary thus becomes the fruit as the 

 ovule has become the seed. 



Sometimes the effect extends still further to other parts of 

 the flower, which thus persist, usually with increased size or 

 change of structure, and form part of what is then termed a 

 pseudocarp or false fruit. In the apple, for instance, the 

 edible portion consists of the greatly developed floral-recep- 

 tacle, which includes the ovary as its core. The ovules are 

 borne usually on some definite part of the ovary wall or walls 

 known as the placenta. They consist of an internal portion, 

 the nucellus, one cell of which grows at the expense of the 

 rest to form an embryo-sac, which again contains the egg-cell 

 or oosphere, and one or two integuments entirely surrounding 



