SPERM ATOPHYTA 67 



1. Into what two families are the cycads divided? De- 

 scribe each briefly, stating one respect in which they resemble each 

 other ; one in which they differ. What is their geologic range ? 



2. Where are cycads living at present ? 



3. Why is the motility of the male cell especially interesting ? 



4. Among what plants was the first flower evolved ? Did 

 it resemble any modern flowers ? What testimony does it 

 furnish upon the origin of the higher flowering plants ? 



5. Sketch Cycadeoidea, labeling bracts, flower buds (if 

 present). What do the bracts represent? Make restoration 

 of entire plant, naming stem, crown of leaves. 



6. What was the age of cycads ? 



Order C, Cordaitales 



An extinct group of tall, slender trees which had a general 

 distribution throughout the world from the Devonian to the Per- 

 mian, inclusive. It is represented by the genus Cordaites. The 

 trunk rose to a height of thirty to one hundred feet and was sur- 

 mounted by a dense crown of branches bearing narrow sword- 

 like leaves. The leaves were distinguished by their conspicuous 

 parallel veins, and their great size, attaining at times a length 

 of three feet. 



The general structure of the stem resembles that of the coni- 

 fers except in the very large pith, which suggests rather that of 

 the cycads. Casts of this pith cavity, called Sternbergia, are 

 common fossils. They are cylindrical bodies, one to four inches 

 in diameter, longitudinally ribbed and m.arked by transverse 

 constrictions at short intervals. The pith in the living stem 

 ruptured transversely at intervals, dividing into disks of solid 

 tissue separated by empty spaces. In the casts of this cavity, 

 where there is a later decay of the pith and w^ood, the position of 

 the pith-disks would be represented by transverse constrictions. 

 This appearance may be seen on a lesser scale in the pith of the 

 walnut, hickory and other common trees to-day. 



The fructifications of Cordaites were small male and female 

 catkins. 



