188 THE SECOND BOOK OF BOTANY. 



is called an indusium. This organ is still more 

 plainly seen in Fig. 350. 



In the sorus (Fig. 350) you see little, peculiar- 

 looking bodies escaping from beneath the indusium. 

 Each of these cell-like bodies, of which the sorus 

 is composed, is known as a spore-case^ sporange, or 

 theca. They are sometimes stalked, as seen in Fig. 

 351. The singular-looking band around them is an 

 elastic membrane, which bursts when they are ma- 

 ture, and thus the spores contained in the spore-case 

 escape (Fig. 351). It is from spores that ferns arise, 

 but by a process more like budding than like the 

 sprouting of a seed. When a spore commences to 

 grow, appearances like those represented in Fig. 352 



may be observed. The growth begun by a spore, 

 as at #, and seen more advanced at 5, is shown, 

 at <?, expanded into a leaf-like body, called a pro- 

 thallus, which gives off roots at the under surface. 

 Among these roots may be found certain bodies, 

 analogous to the stamens and pistils of flowers, and 

 called the antheridia and pistillidia. It is not until 

 these bodies have matured and done their work that 

 the young fern appears. If there is any thing like 



