LYCOPODIALES ^^17 



The LYCOPODIALES, to which Selaginella belongs, are Vascular Plants 

 with relatively small leaves (microphyllous), borne upon an axis which 

 is usually branched profusely, and rooted in the soil. The branching 

 is by forking (dichotomy) both of root and stem. But there is frequent 

 transition to mono po dial brafic king, that is by outgrowth of the branch, 

 or root, laterally below the apex of the original part. Dichotomy 

 IS prevalent also in their early fossil relatives, and is frequent among 

 plants lower in the scale of organisation. More or less definite cones 



Fig. 25S. 

 Partof the shoot of Selaginella Martensii, showing its " espalier " form, and uiinutc 

 unequal leaves. It is seen from above, and the forking rhizophcres arc directed 

 downwards. (Nat. size.) (After Goebel, from Strasburger.) 



or strohili are borne at the ends of the branches. Compressed in the 

 axil of each leaf of the cone is a single sporangium, that opens when 

 ripe like an oyster, by a marginal slit. These characters of the 

 sporangium are common for the Lycopodiales, modern and ancient. 



The Lycopodiales are represented in the British Flora by one species 

 of Selaginella (S. spinulosa). But over 300 other species of the genus are 

 widely spread, chiefly in the tropical zone, and many are in cultivation. 

 They are mostly low-growing, and often shade-loving and straggling 

 plants (Fig. 258). Another British representative is a curious inhabi- 

 tant of fresh-water lochs, Isoetes lacustris, with its long leaves crowded 



