20 



PROPAGATION, DEVELOPMENT, AND CULTURE. 



NATURALLY Perns are propagated by means of the spores, 

 of which mention has been already made. These spores 

 are somewhat analogous to seeds, being like them endowed 

 with that mystery the vital germ ; and, when placed under 

 fitting conditions, they become developed into young plants ; 

 but they differ from seeds in some important particulars. 



All true seeds have a determinate structure; they have 

 an embryo, with special organs, namely, the plumule, or 

 germ of the ascending axis, the origin of the stem, and 

 the radicle, or germ of the descending axis, the origin of 

 the root. When a seed is planted, in whatever position it 

 may chance to have been deposited in the soil, the young 

 root or radicle strikes downwards, and the young stem or 

 plumule grows upwards. 



The Tern spores have none of these determinate parts, 

 but are, as it were, homogeneous atoms ; and when placed 

 under circumstances which induce germination, that part 

 which lies downwards produces the root, and that part 



