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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 LycopopINEAE) 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 (516. 141 bycopodium 
there is one on the upper surface of sperms, archegones and | 
egg.) 
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- 
| 
| 
Ww" Pa 
zoic period have been recorded. 
478. Inthesecond class are the Club-mosses 
®o9 (Family Selaginellaceae) which resemble the 
Fre. 142-- Ground Pines, but in our common species are 
(ycopodium generally smaller and more moss-like, and 
sees 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) 
