2 GERMINATION 



prothallus is formed, in which one or more archegonia arise. 

 These are exposed to the exterior by the bursting of the 

 coats of the macrospore, and are fertilised by the sperma- 

 tozoids in the usual way. 



As the prothallus is, in effect, a genital organ, it follows 

 that the process is essentially the same in both animal and 

 plant. The main difference appears to be that with the first 

 the act is a conscious one and in the second, so far as we 

 know, unconscious. 



Lord Avebury, in his work on Seedlings, says : " The seed 

 is the result of the fertilisation of the ovule by the pollen. 

 The effect of fertilisation, however, extends in the angio- 

 sperms beyond the ovules to the ovary in which they are 

 contained. The ovary thus becomes the fruit, as the 

 ovule has become the seed. In the apple, for instance, 

 the edible portion consists of the greatly developed floral 

 receptacle, 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 the nucellus, except at the apex where 

 a small aperture, known as the micropyle, is left. In the 

 process of fertilisation the pollentube passes down the 

 micropyle to the oosphere, which, enclosed in the embrj^o-sac, 

 approaches very close to the outer wall of the ovule at this 

 point. After fertilisation the oosphere developes into the 

 embryo, the rest of the embryo-sac becoming filled with a 

 cellular tissue, the endosperm." 



That, I think, is sufficiently descriptive of the principle 

 involved but there is, as may be imagined, considerable 

 variety in the position and arrangement of the ovule and 

 subsequently of the seed. 



And here is a point I should like to make. 



Strasburger remarks that it is the non-motile egg-cells, or 

 female sexual organs of plants which exert an attractive 

 influence upon the motile male cells, but adds that when 

 there is no difference in the external form of the male and 



