424 SYSTEMATIC BOTANY. 



by Fankhauser with one of them already attached to the young spore- 

 hearing generation. They possess root-hairs, and are self-supporting arid 

 monoecious. Antheridia containing numerous spermatozoids are formed 

 abundantly on the upper surface of the prothallium, on which side the 

 archegonia also are situated. Of the phases in the development of the 

 embryo nothing is known. 



Affinities, &c. The immediate relations of this Order are with the 

 Selaginellaceae. 



Distribution. The species of Lycopodium are widely diffused through- 

 out the world, but are most abundant in warm countries. Five species 

 are natives of Britain. Psilotum is a native of the tropics of both hemi- 

 spheres and of Australia. In former ages the species of this Order seem 

 to have attained much greater dimensions than they have at present. 

 The fossil stems known as Lepidodendron are like existing Tree Ferns, 

 but their fructification is that of Lycopods. Thpy existed in such abun- 

 dance in the Carboniferous times that some varieties of coal are stated 

 to be almost entirely composed of their remains. Lepidostrobus is the 

 fruiting spike of some Lycopod. 



Qualities and Uses. It is asserted that some kinds of Lycopodium are 

 poisonous. L. damtum has been used as an emetic. L. Selago and L. 

 catharticiim are purgatives ; the latter is very violent in its action. The 

 powder known in pharmacies as Lycopodium consists of the spores of a 

 species of this genus. They are very inflammable, and are hence used 

 for theatrical purposes ; and as they no not absorb water readily, they are 

 used for covering the hands &c. when it is desired that they be not 

 wetted. 



Series 2. HETEEOSPOEIA. 



Vascular Cryptogams producing spores of two kinds, macro- 

 spores and microspores. The macrospores develop a female 

 prothalliuui, which remains attached to the spore ; the microspores 

 produce a rudimentary male prothallium, which remains attached 

 to the spore and develops anthericlia and antherozoids. 



In the three preceding Orders (Equisetaceae, Filices, and Lycopodiacese) 

 the prothallia arise from spores of one kind. In the two following Orders 

 (Selaginellaceee and Rhizocarpese) the female prothallia are produced by 

 macrospores, and the male prothallia by microspores. The prothallia are 

 also different in their nature. In the three preceding Orders the prothal- 

 Jium is self-supporting, and possesses completely the character of an 

 independent plant. In the two following Orders the prothallium is 

 no longer an independent plant, since it is formed within the spore, and 

 at no period breaks connexion with it. 



SELAGINELLACEJE. 



Diagnosis. Asexual Generation : In Selaginella the stem is thin, 

 dichotomously branched, bearing small heart-shaped appressed 



