GROUND PINES 



267 



walled fibrous tissue. The epidermis is abundantly 

 supplied with stomata. 



476. The phylum contains about 700 living species, 

 and consists of two quite distinct classes, viz.: The 

 Lower Lycopods (Class Lycopodineae) mainly dis- 

 tinguished by being isosporous, and the Higher Lycopods 

 (Class Lepidodendrineae) which are heterosporous. 



477. In the first we find the Ground Pines (Family 

 Lycopodiaceae) , otherwise known as Club-mosses, which 

 are terrestrial, perennial, evergreen plants with many 

 small, generally moss-like leaves cover- 

 ing the stems. The sporophylls are 

 often crowded toward the summits of 

 certain branches, in some cases form- 

 ing well-marked cones (strobili) . The 

 spores are all of one kind, and are 

 borne in roundish sporangia of which 

 there is one on the upper surface of 8pe™3, "archegones and 

 each leaf near the base. 



The Ground Pines are common in the Appa- 

 lachian region, Canada, and northwestward, and all 

 belong to the genus Lycopodium, including L. clavatum, 

 L. complanatum and L. dendroideum, all ex- 

 tensively used in Christmas decorations. Fos- 

 sil specimens of Ground Pines from the Paleo- 

 zoic period have been recorded. 



478. In the second class are the Club-mosses 

 (Family Selaginellaceae) which resemble the 

 Ground Pines, but in our common species are 

 generally smaller and more moss-like, and 

 have (with few exceptions) four-ranked leaves. 

 Their sporangia occur singly on the sporophylls 

 which are clustered into terminal spikes (cones). The 

 spores are of two kinds: the small ones (microspores) 



Fig. 141. — ^Lycopodium 

 (gametophyte, antherids, 



Fig. 142.— 

 Lycopodium 

 (sporophyte, 



s p o r a n g ia. 



Spores). 



