34 OUR NATIVE FERNS AND THEIR ALLIES. 



LITERATURE. 



BAKER (J. G.). Fern Allies, pp. 1-6 (1887). 



BRAUN (Alexander). A Monography of the North American 

 Species of the Genus Equisetum. With additions by George 

 Engelmann, M.D. In Silliman's Journal, XLVI, 81-91 (1843). 

 Describes the then known North American species of Equisetum. 



CAMPBELL (Douglas H.). - The Development of the Male 

 Prothallium of the Field Horse-tail. In American Naturalist, 

 xvi, i-io (Jan. 1883). 



MILDE (J.). Monographia Equisetorum. 410, pp. 607, with 

 35 plates. Dresden (1865). This elegant work is a marvel of 

 completeness, and a monument to the patience, industry, and 

 ability of the author. 



C. THE CLUB-MOSSES. 



92. General Characters. The club-mosses are chiefly 

 small perennial plants usually growing in dry or moist woods, 



or even on exposed rocks 

 with little soil for nourish- 

 ment. Most of the species 

 are somewhat moss-like in 

 habit, as might be suspected 

 from the popular names 

 given to these plants, the 

 genus Lycopodium taking 

 the name of club-moss and 

 Selaginella that of rock- 

 moss. Various species of 

 Lycopodium are also known 

 as ground-pine, ground-fir, 

 ground-cedar, running pine, 

 etc., from more or less 

 marked resemblances (Fig. 

 23). In the curious Sela- 

 ginella lepidophylla from 



FIG. 23. Portion of Lycopodium clavatum L. . . - , 



^ natural size. (After Prantl.) Arizona the branches of the 



closely coiled central stem roll up when dry into a nest-like 

 ball, and when moistened expand so as to appear flat or saucer- 



