LYCOPODIAU-.S 



513 



But most living species have a much-branched, dorsiventral shoot of 



an " espalier " type, sometimes simulating highly compound lea- 

 (Fig. 405). On these shoots the actual leaves are disposed in four 

 longitudinal rows, those on the lower Hanks being larger, those on the 

 upper smaller. Such shoots are commonly propped up by root-like 

 organs (rhizophores) borne at the forkings of the shoot, and themselves 

 showing very regular dichotomy. They are not actually roots, but 



Fig. 404 b. 



Plant of Selaginella spinulosa, with root-system springing from swollen knot at base of 

 the upright hypocotyl. Here there are no rhizophores. Natural size. 



on reaching the ground they give rise to roots endogenously : hence 

 their name. Structurally Selaginella is relatively simple. The 

 vascular system is. essentially of the same type as in simple Ferns. 

 It consists of sharply circumscribed stelar tracts, with tracheides but 

 no vessels, and peripheral phloem. Each is surrounded by an endo- 

 dermis, which in many species shows the cell- laterally separated as 

 radiating " trabeculac." In the smaller species the stele remains 

 simple, but in some of the larger it may be disintegrated, somewhat 



