594 



STRUCTURE AND LIFE HISTORIES 



divided fronds with small, thick pinnules with revolute 

 margins, suggesting a xerophytic or halophytic habitat. 

 The stem in the lower portion gave rise to numbers 

 of slender roots, some of which appear to have been 

 aerial in their origin. These grew downward and often 

 branched where they entered the soil. 



Fig. 416. — Young leaf of the Cycad, Bowenia serrulata. Comparison 

 of this with a leaf of the fern Angiopleris (Fig. 417) shows how difficult 

 it might be to decide from a fossil leaf whether the plant was a cycad or a 

 fern. (Cf., also, Fig. .420.) 



"The stems, roots, and petioles, and even the pinnules, 

 have been found silicified and so beautifully preserved that 

 their entire structure can be made out with certainty. 

 Without going into a technical description of these organs, 

 it may be said that the stem when young, and before 

 secondary growth has begun, has a very strong resemblance 



