714 



THE SUBDIVISIONS OF THE VEGETABLE KINGDOM. 



the latter their condition parallels that of the Hydropterides. Lepidodendraceae 

 and SigillariaceiE are represented by fossil forms only. 



Lycopodiaeece. — The Club-mosses proper include some 100 species, distributed 

 over various parts of the globe. The habit of a typical Lycopodium is indicated in 

 the accompanying figure of L. annotinum, with its branching stem closely set with 

 simple, scale -like leaves and terminal cones. The species common in mountain 

 regions in this country are L. clavatum, L. alpinuTti, and L. Selago; L. annotinum. 



Fig. 404. — Lycopodium annotinum, 



(fig. 404) is also met with. Of these L. Selago alone is devoid of cones, its sporangia 

 occurring on the ordinary leaves. The sporangium is generally large and kidney- 

 shaped, and is attached to the base of the upper side of the leaf (fig. 405*); its 

 concavity is directed towards the axil of the leaf. Till recently the life-history of 

 Lycopodium was unknown, as difficulty was experienced in causing the spores to 

 germinate. It was first observed in certain tropical species, L. cernuum and others. 

 In this species the prothallium has the form of a tiny tuberous body, with a lobed 

 fringe on which the antheridia and archegonia are developed. The history of 

 development of the sporophyte from the egg has been followed and is of some 

 interest. In L. cernuum the young plant consists of a tubercle bearing a tuft of 



