200 



A TEXT-BOOK OF BOTANY 



B 



loosen and uncoil; when moistened, they close around the 

 spore. The coiling and uncoiling movements of these bands 



as they are wet 

 or dry entan- 

 gle the spores, 

 and they fall in 

 clumps, a num- 

 ber of them 

 thus germinat- 

 ing close to- 



FIG. 192. A, a sporophyll of Equisetum, bearing sporangia pother 

 beneath the shield-like top; B and C, spores, showing 

 the unwinding of the two bands forming the outer coat. 114. GametO- 



phyte. When 



the spores of an Equisetum germinate they give rise to 

 gametophytes that in all general features resemble those of 

 the ferns; that is, they are small, green thallus bodies pro- 

 ducing antheridia and archegonia. From the oospores pro- 

 duced in the archegonia the large sporophyte arises, with 

 its roots, xootstock, branches, leaves, and strobili. 



It is evident that, although an Equisetum does not 

 seem to resemble a fern in the least, the life-history and 

 the character of the alternating generations are the same. 



CLUB-MOSSES 



115. General characters. The club-mosses often look 

 like coarse mosses, as the name suggests. Some of the 

 larger ones are called also ground pines, because of a cer- 

 tain resemblance to miniature pines. They are slender 

 branching plants, with the prostrate or erect stems com- 

 pletely clothed with small leaves (Fig. 193). The larger 

 and coarser forms are abundant in the Northern woods, the 

 prostrate stems often trailing extensively and giving rise to 

 erect branches. The more delicate forms are abundant 

 in the tropics, and are very common in greenhouses as 

 decorative plants. 



