286 



ESSENTIALS OF BOTANY 



is shown in the diagram (Fig. 208). In the mosses and 

 their allies the full-grown plant is a gametophyte, and the 

 spore-bearing plant or sporophyte appears as a sort of par- 

 asitic outgrowth of the 

 gametophyte (Sect. 357). 

 In the ferns and their 

 allies the full-grown 

 plant (that which we com- 

 monly call a fern) is an 

 asexual sporophyte, am- 

 ply provided with vege- 

 tative organs, i.e. roots, 

 stem, and leaves, often 

 capable of living for 

 many years and attain- 

 ing the dimensions of a 

 tree. The gametophyte 

 (prothallium) in ferns is 

 a minute, usually short- 

 lived structure, and ex- 

 ists simply to mature an 

 egg which may produce 

 a fern-plant. 



366. Summary of the 

 Ferns. — Most ferns are 

 land plants, but there 

 is one order of aquatic 

 ferns, some of which live 

 floating freely in water and others grow rooted in the 

 mud. Ferns vary greatly in size, the smallest genera not 

 being nearly as large as some mosses, while others are tree- 

 like. With abundant vessels, rigid tissue for strengthening 



~EiG. 209. Sensitive Tern (Onoclea). 



s, sterile or vegetative frond ; /, fertile frond 

 or sporophyll. 



