SEX AND HEREDITY 



are not liberated, nor do the archegonia open. It is 

 possible by watering cultures only by absorption from 

 below to grow the sexual plants of Ferns or Mosses for 

 long periods without any sexual propagation at all. 

 This is a restricted existence from which the Higher 

 Land-living Plants have finally broken away. In the 



FIG. 18. 



Kmtryo of a Fern (Adia;itiiin\ embedded in the tissues of the parent prothaUus. 

 where it is protected and fed by the surrounding tissues. L = leaf; .K = ro >t : 

 S = stem; F = suctoria! foot. (After Atkinson.) 



Seed-Plants, as we shall see, external fluid water is no 

 longer necessary for syngamy. 



In the previous Lecture it has been seen that the bare 

 facts of syngamy in Flowering Plants correspond to those 

 in lower forms. The male gamete is produced from 

 the pollen-grain. The female gamete, or egg, lies deeply- 

 seated in the ovule. These gametes fuse together to 

 form a zygote that develops into the embryo. But as 



