SPERMATOPIIYTES: GYMNOSPERMS 



189 



extinct ones. The groups differ so widely from one an- 

 other in habit as to show that Gymnosperms can be very 

 much diversified. They are all woody forms, but they may 

 be trailing or straggling 

 shrubs, gigantic trees, or 

 high-climbing vines ; and 

 their leaves may be nee- 

 dle-like, broad, or "fern- 

 like." For our purpose it 

 will be only necessary to 

 define the two most prom- 

 inent groups. 



105. Cycads. Cycads 

 are tropical, fern - like 

 forms, with large branched 

 (compound) leaves. The 



stem is either a columnar 



shaft crowned with a ro- 

 sette of great branching 



leaves, with the general 



habit of tree-ferns and 



palms (Figs. 155, 156); 



or they are like great tu- 

 bers, crowned in the same 



way. In ancient times 



(the Mesozoic) they were 



very abundant, forming 



a conspicuous feature of 



the vegetation, but now 



they are represented only 



by about eighty forms 



scattered through both 



the oriental and occiden- 

 tal tropics. PIG. 159. The giant redwood (Sequoia gi- 

 Thpv flrp vprv fprn gantea) of California : the relative size 

 lie J is indicated by the figure of a man stand- 



like in Structure as well ing at the right. After WILWAWBON. 



