i28 STUDIES IN FOSSIL BOTANY 



Carboniferous period, and dying out, according to our 

 present knowledge, in the Permian. These plants had 

 much the same habit as the Lycopodia of the present 

 day, but enormously exceeded them in dimensions, 

 growing into large trees, of which trunks a hundred 

 feet long have been found. The main stem was vertical, 

 rising to a great height before the crown of branches 

 was reached (see restoration, Fig! 52). The ramifica- 

 tion was constantly dichotomous ; the two limbs of the 

 dichotomy were sometimes equal, as in the forking of 

 the main branches, but were often very unequal ; t in 

 the latter case the relatively main shoots formed a 

 sympodium, the smaller members of the successive 

 dichotomies simulating lateral branches (Fig. 52). The 

 whole system of ramification was thus an exceedingly 

 complex one, built up of branches of many degrees, 

 and differing much from each other, not only in size, 

 but in structure — a fact which is of great importance 

 in dealing with the comparative anatomy of trunks 

 and twigs. 



The young stems and branches were densely clothed 

 with numerous simple leaves of acicular or linear form 

 (Fig. 53), and sometimes of great length, amounting 

 in certain cases to as much as 6 or 7 inches. The 

 phyllotaxis was either a close spiral with some very 

 complex divergence, such as ■^ s , or consisted of a 

 system of whorls, the members of successive whorls 

 having themselves a complicated spiral arrangement. 



When the leaves were shed, their bases remained 

 attached to the surface of the stem, forming the leaf- 

 cushions (Fig. S3, A), which were persistent even on 

 the larger trunks. It is chiefly on the superficial 



