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- 



