^i8 



BOTANY OF THE LIVING PLANT 



upon a short succulent stock, which is fixed by dichotomous roots in 

 the mud at the bottom. Others are the Club Mosses [Lycopodium), 

 of which some five species grow on heaths and moors, chiefly in hilly 

 districts ; while nearly 1 00 other species are widely spread through 

 the tropics and temperate zones. They also are low-growing plants, 



and some are epiphytes. These 

 inconspicuous plants are the meagre 

 present-day representatives of a 

 type which grew to tree-like size in 

 the Coal Period, and contributed 

 largely to the organic remains pre- 

 served as Coal. 



The Lycopodiales are divided into 

 two Series, the Ligulatae, which include 

 Selaginella and Isoetes, and most of tlie 

 early fossil types. They are character- 

 ised bv a minute scale, or ligule, 

 borne on the upper surface of each 

 leaf near its base (Figs. 260, 261) The 

 Eligiilatae have no ligule. They include 

 the Club-Mosses {Lvcopodium], and 

 some of the early fossils. 



Selaginella. 



The primitive type of Selaginella 

 had upright radial axes, with leaves 

 of equal size all round it ; and this 

 is the case in S. spinulosa. But 

 most of the species have a much- 

 branched, dorsiventral shoot of an 

 Fig. 259. "espalier" type, sometimes simu- 



SdagineUa. inaeguali/olia. A, fertile braneh [^^^[^p highly COmpOUnd IcaVCS (Fig. 



half natural size. B, its tip in longitudinal b b J f \ a 



section, with microsporangia to the left, and 3^8) On tlieSC shoOtS the actual 



niegasporangia to the right. (After Sachs.) •' ' . . 



leaves are disposed in four longi- 

 tudinal rows, those on the lower flanks 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 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 that to be described 



