CLASSIFICATION OF THE PTERIDOPHYTES. 123 



CLASS III. THE CLUB MOSSES (Lycopodince) . 



The last class of the pteridophytes includes the ground 

 pines, club mosses, etc., and among cultivated plants numerous 

 species of the smaller club mosses (Selaginelld). 



Two orders are generally recognized, although there is some 

 doubt as to the relationship of the members of the second 

 order. The first order, the larger club mosses (Lycopodiacece) 

 is represented in the northern states by a single genus (Lyco- 

 podium), of which the common ground pine (L. dendroideum) 

 (Fig. 73) is a familiar species. The plant grows in the ever- 

 green forests of the northern United States as well as in the 

 mountains further south, and in the larger northern cities is 

 often sold in large quantities at the holidays for decorating. 

 It sends up from a creeping, woody, subterranean stem, numer- 

 ous smaller stems which branch extensively, and are thickly 

 set with small moss-like leaves, the whole looking much like 

 a little tree. At the ends of some of the branches are small 

 cones (A, x, B) composed of closely overlapping, scale-like 

 leaves, much as in a fir cone. Near the base, on the inner 

 surface of each of these scales, is a kidney-shaped capsule 

 (C, sp.) opening by a cleft along the upper edge and filled 

 with a mass of fine yellow powder. These capsules are the 

 spore cases. 



The bases of the upright stems are almost bare, but become 

 covered with leaves higher up. The leaves are in shape like 

 those of a moss, but are thicker. The spore-bearing leaves are 

 broader and when slightly magnified show a toothed margin. 



The stem is traversed by a central nbro-vascular cylinder 

 that separates easily from the surrounding tissue, owing to the 

 rupture of the cells of the bundle sheath, this being particu- 

 larly frequent in dried specimens. When slightly magnified 

 the arrangement of the tissues may be seen (Fig. 73, E). 

 Within the epidermis is a mass of ground tissue of firm, 

 woody texture surrounding the central oval or circular fibro- 



