Ch. XII] 



THE SELAGINELLAS 



505 



seminated by wind. These spores are very light and happen 

 to be also very inflammable, on which account they have been 

 used somewhat in fireworks, under the name " vegetable 

 sulphur." They germinate to prothallia which are re- 

 markably diverse in the different species, some being green, 

 and others partially so (Fig. 358). Others are completely 

 buried in the ground, tuberous, symbiotic 

 with mycorhizal fungus, much as in case <^SflHBh~u. 

 of Ophioglossum (page 495). Archegonia 

 and antheridia are sunken in the pro- { 

 thallus, and the free-swimming sperm 

 cells are biciliate, as in Liverworts. The 

 fertilized egg cell germinates to an embryo 

 having a suspensor as in the Spermato- 

 phytes, and remains buried in the pro- 

 thallus until well developed, — other 

 features which bring these plants very 

 close to the Spermatophytes. 



Fig. 358.— Prothal- 

 lus of Lycopodium 

 complanatum, in opti- 

 cal section ; X 10. 



The lower portion is 

 tuberous and subter- 

 ranean, and the upper 

 is above ground. In 

 the latter can be seen 

 archegonia, anthe- 

 ridia, and an embryo. 

 (After Bruchmann.) 



Order 2. Selaginellales : the Sel- 

 aginellas or llttle club mosses. 

 These resemble in general the Lycopo- 

 diales, but are more delicate and graceful. 

 They abound most in the tropical regions. 

 Their leaves occur usually in horizontal 

 ranks, suggesting the Leafy Liverworts, 

 for which our native species might readily 

 be mistaken. Many of the species 

 possess a unique structural feature in the rhizophores, 

 which are leafless stem-like structures springing from the 

 under sides of the stems, and developing roots when they 

 enter the ground. While most of the species are terrestrial, 

 some are partly climbing or epiphytic. An interesting form, 

 rather familiar because often sold by itinerant vendors, is the 

 Resurrection Plant 'Selaginella lepidophylla) , a rosette 

 form which clones to 2 compact ball when dried, and opens 



