lo6 THE CHAIN OF LIFE. 



the Polypod type, which is the most common at present, but 

 to certain comparatively rare southern ferns, the Marattias and 

 their allies, characterised by a peculiar style of fructifica- 

 tion, pei iiaps adapting them to a moist and warm atmosphere 

 (Fig. 97).i Thus the ferns, while a wonderfully persistent type, 

 were in their grander forms far more widely distributed in the 

 Carboniferous than at present ; and genera now comparatively 

 rare, and limited to warm and moist climates, were then abun- 

 dant, and ranged over those temperate and boreal regions of 

 the Northern Hemisphere where only a few humble and hardy 

 species can now subsist. There were also some remarkable 

 and anomalous tree-ferns, of which that represented in Fig. 98 

 is an example. 



The family of the Club-mosses, already, even in :he Devonian, 

 in advance of its modern development, exper js in the Car- 

 boniferous a remarkable and portentous extension into great 

 trees of several genera and many species, constituting apparently 

 extensive forests, and having the woody tissues of their stems 

 developed to a degree unheard of in their present representatives 

 (Fig. 99). Further, they become closely linked, in external form 

 at least, with another and more advanced type, that of the 

 Sigillarice. These remarkable trees were the most abundant 

 of all in the swamps of the coal-formation, and probably those 

 which most contributed to the accumulation of coal. They 

 presented tall pillar-like trunks, often ribbed longitudinally, and 

 with perpendicular rows of scars of fallen leaves. Dividing at 

 top into a few thick branches, they were covered with long 

 rigid grass-like foliage. Their fiuit was borne in rings or 

 whorls of spikes surrounding the branches at intervals (Fig. 

 160). Their roots were strangely symmetri-^al, spreading out 

 like underground branches into the soft soil by a regular pro- 

 cess of bifurcation, and were covered with rootlets diverging 

 in every direction, and so jointed to the main root that when 



* Grand' Fury and Williamson have directed attention to this in the case 

 of those of France and England. _ 



