204 



CRYPTOGAMS 



growth called the protonema, which' spreads over the soil 

 and resembles a filamentous Green Alga. Finally shoots 

 appear as buds on the protonema (Fig. 343). 



476. It will be noticed that in the Bryophytes (Liver- 

 worts and Mosses) the fertilization of the egg cell does 

 not, as in most Algse, produce an oospore which separates 

 from the parent and develops into a new and distinct 

 plant. The fertilized egg remains in position in the 

 archegonium and gives rise to the spore-producing organ, 

 or sporogonium. 



FERNS AND FERN ALLIES (PTERIDOPHYTES) 



477. Most of the Ferns and Fern allies of to-day are 

 comparatively small plants, frequently with a creeping 

 habit; some grow partly or wholly submerged; while 

 several small species are floating plants. All this is in 

 strong contrast with conditions in former geological times. 

 In the Coal period Tree Ferns (now confined to the 



tropics) were widely distributed. 

 Certain relatives of the modern 

 slender, creeping Club Mosses (Fig. 

 357) were trees from 60 to 80 feet 

 in height. Similarly some Equise- 

 tumlike plants, now represented 

 mainly by species from 1 to 4 or 5 

 feet tall (Fig. 358) were tolerably 

 stout trees 30 feet high. Forests 

 largely composed of these Crypto- 

 gams formed the immense coal de- 

 posits of that period. 



478. Ferns are still numerous, and 

 in some places are predominant fea- 

 tures of the vegetation. In the 

 tropics they are especially abundant 



344. A tropical Tree Fern. an d l ar g e (Fig. 344). I n mos t com- 

 mon species the stem is a creeping 



rhizome (Fig. 345), wholly or partly buried, so that all 

 that one sees is the foliage rising from the ground. Ferns 



