MOSSES, LIVERWORTS, AND FERNS 



279 



Modern equisetums live about open marshes, in sandy 

 wastes, and along railroad embankments. They have hard, 

 rough, siliceous stems, 

 with small leaves that 

 form sheaths about the 

 joints of the stem (fig. 

 217). In the most com- 

 mon species of Equisetum 

 the sporophyll branch 

 appears very early in the 

 spring and produces at 

 its tip the strobilus, or 

 cone, which bears the 

 sporangia upon greatly 

 reduced and transformed 

 leaves (sporophylls). The 

 bushy chlorophyll branch 

 appears later and is the 

 one which grows through- 

 out the season, the sporo- 

 phyll branch disappearing 

 as soon as the spores have 

 been shed. The spores 

 are attached to pecul- 

 iar strap-like outgrowths 

 known as elaters (driv- 

 ers). The elaters are 

 supposed to assist in dis- 

 tributing the spores. 



The bushy foliage, or 

 chlorophyll part of the 

 plant, grows and depos- 

 its food material which 

 may be used the next 

 season for the growth of 

 the sporophyll branch. 



Fio. 218. A club moss (Lycopodiuni) 



The horizontal rootstoek, with its roots, grows 

 within or upon the humus. The upright branches 

 (A) hear green leaves and strobili (str) (also 

 called spikes or cones) in which spores are 

 formed. At 6' is shown one leaf from the strobi- 

 lus, and upon this leaf is a sporangium. From 

 the partially opened sporangium, spores escape. 

 /.' shows enlarged spores 



