STUDIES IN CRYPTOGAMS 



20I 



strand of tissue, the columella, which expands at the mouth into a 

 thin, membranous disl<, closing the entire mouth of the capsule 

 except the narrow annular chink guarded by the 

 teeth. In this moss the points of the teeth are 

 attached to the margin of the membrane, allow- 

 ing the spores to sift out through the spaces be- 

 tween them. 



When the spores germinate they form a green, 

 branched thread, the protonema. This gives rise 

 directly to moss plants, which appear as little 

 buds on the thread. When the moss plants have 

 sent their little rhizoids into the earth, the pro- 

 tonema dies, for it is no longer necessary for the 

 support of the little plants, and the moss plants 

 grow independently. 



Fimaria is a moss very common on damp, 

 open soil. It forms green patches of small fine 

 leaves from which arise long brown stalks termi- 

 nated by curved capsules (Fig. 298). The struc- 

 ture is similar to that of polytrichum, except the 

 absence of plates on the under side of the leaves, 

 the continuous growth of the stem, the curved 

 capsule, double peristome, monoecious rather than dioecious re- 

 ceptacles, and nearly glabrous unsymnietrical calyptra. 



Fig. 298. — Fu- 



NARIA HY- 

 GROSCOPICA. 



Equisetums, or Horsetails (Pteridophyta) 



There are about twenty-five species of equisetum, constituting 

 the only genus of the unique family Equisetacece. Among these 

 E. arvetise (Fig. 299) is common on clayey and sandy soils. 



In this species the work of nutrition and that of spore 

 production are performed by separate shoots from an underground 

 rhizome. The fertile branches appear early in spring. The stem, 

 which is 3 to 6 inches high, consists of a number of cylindrical, 

 furrowed internodes, each sheathed at the base by a circle of scale 

 leaves. The shoots are of a pale yellow colour. They contain no 

 chlorophyll, and are nourished by the food stored in the rhizome 

 (Fig. 299). 



The spores are formed on specially developed fertile leaves or 

 sporophylls which are collected into a spike or cone at the end of 

 the stalk {a, Fig. 299). A single sporophyll is shown at b. It 

 consists of a short stalk expanded into a broad, mushroom-like 

 head. Several large sporangia are borne on its under side. The 

 spores formed in the sporangia are very interesting and beautiful 



