294 



PRACTICAL BOTANY 



their chlorophyll. These sporophylls are closely appressed 

 (Fig. 245), thus forming a dense cone. In a few species the 



sporophylls are loosely 

 arranged. In the axils 

 of leaves sporangia are 

 formed, and in these are 

 large numbers of asex- 

 ual spores. So numer- 

 ous and so light are 

 these spores that they 

 have been used as the 

 commercial article now 

 known as Lycopodium 

 powder. When these 

 spores germinate they 

 produce underground 

 tuberous gametophytes, 

 upon one of which both 

 sex organs may form. 

 Fertilization, which is 

 extremely difficult to 

 study in this genus, 

 occurs underground. 

 The oospore produces 

 the young sporophyte, 

 which grows up from 

 the ground somewhat 

 as does the seedling of 

 higher plants. 



The reproduction of 

 Selaginella differs from 

 that of Lycopodium in 

 the important fact that 

 the asexual spores are 

 of two kinds, one very 

 small and one very large. 



Fig. 245. A club moss, or ground pine 

 {Lycopodium) 



The horizontal rootstock witli its roots grows 

 within or upon the humus. The upright branches 

 (A) bear green leaves and strobili (str), also 

 called spikes or cones, in which spores are formed. 

 At C is shown one leaf from the strobilus, and 

 upon this leaf is a sporangium. From the par- 

 tially opened sporangium spores escape. At B 

 enlarged spores are shown 



