DEVELOPMENT OF PLANTS 



343 



strobili at the tips of certain branches. But a single sporangium 

 is associated with each of these sporophylls (Fig. 239). 



The club mosses are a very much larger group than the Equise- 

 tales, but like the latter group, they are a remnant of a highly 

 developed and widely distributed race. Fossil remains indicate 

 that the ancient allies of these plants were conspicuous features 

 of an earlier vegetation, with palm-like trunks 100 feet in height 

 and three feet in diameter, and bearing a crown of long narrow 

 leaves that attained a length of three feet. They reached their 



Fig. 238. Fig. 239. 



Fig. 238. Phylloglossum Dnimmondi. — After Pritzcl. 



Fig. 239. Strobilus and sporophylls of Lycopodium: 2, strobilus. 3, a 

 leaf or sporophyll from the strobilus enlarged and showing attached spo- 

 rangium, 4, a spore greatly magnified. 



greatest abundance in the coal age and thence gradually declined, 

 being crowded out by the more specialized seed plants. There 

 are two important families of the Lycopodiales: i, Lycopodiaceae; 

 2, Selaginellaceae. 



116. Family i. Lycopodiaceae. — With but one exception the 

 members of this family belong to the genus Lycopodium, com- 

 monly known as the club moss, ground or running pine, ground 



