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 

 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 

 <5 a (Family Selaginellaceae) which resemble the 

 Ground Pines, but in our common species are 

 generally smaller and more moss-like, and 

 lpore r s) angia ' h ave (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) 



