THE CONE OF LYCOPODIUM 



331 



321. The cone of Lycopodium. In some species of 



as L. Selago, the spore leaves (sporophylls) have the 

 same form and grouping as the vegetative leaves so that there 

 is no cone distinct from the rest of the stem. But most of the 

 forms have very clearly defined cones, which are sometimes raised 

 on long stalks, as in L. compla- 

 natum. The sporophylls are 

 generally scale-like and closely 

 set (Fig. 287, A, B). Each spore 

 leaf bears a single, large, sac-like 

 sporangium (Fig. 287, C) at its 

 base, which develops from a 

 group of cells. The spores (Fig. 

 287, D) are formed in groups 

 of four (tetrads) in the spore 

 mother cells. They are very 

 minute and are produced in such 

 immense numbers that they are 

 collected in quantity as the 

 lycopodium powder of apothe- 

 cary shops, used in dusting 

 pills to keep them from sticking 

 together as well as for other 

 purposes. This powder is also 

 employed in the manufacture 

 of fireworks under the name of 

 vegetable sulphur. 



322. The gametophytes of 

 Lycopodium. The gametophytes 



of the club mosses in our northern woods must be uncommon, if 

 they are developed at all, for they have never been found. It is 

 probable that the sporophy tes reproduce chiefly or perhaps entirely 

 by vegetative brandling of their stems and in some forms by 

 curious buds. The gametophytes of some tropical lycopods are 

 however known and have been studied. They are small, tuberous 



FIG. 287. The cone of a club moss 

 (Lycopodium annotinum) 



4, the cone, showing overlapping sporo- 

 phylls; i>, diagram of a longitudinal 

 section, illustrating the form and 

 position of the sporophylls and spo- 

 rangia ; C, the inner face of a sporo- 

 phyll, showing the large sporangium ; 

 .D, two views of spores from a group 

 of four (tetrad) 



