CALAMITES AND LYCOPODS 
377 
prefer a substratum rich in humus or other organic matter. 
Most of the species are restricted to one hemisphere, but 
a few occur in both. 
338. The Sporophyte. There are several hundred 
species of Lycopodium. Among those most common in 
temperate America are L. clavatum (Fig. 272), L. obscurum 
FIG. 272. Lycopodium clavatum. 
dendroideum, and L. lucidulum. These species commonly 
grow trailing over the surface of the ground, and from 
this, and the appearance of their foliage, they are com- 
monly called "ground pine," though of course they have 
nothing to do with true pines. As is well shown in the 
figure, the plant-body of the sporophyte of Lycopodium 
clavatum consists of a sterile lower region, bearing foliage- 
