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. 
FfG. 416. Young leaf of the Cycad, Bou'enia scrrulata. Comparison 
of this with a leaf of the fern Angiopteris (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 [calcined] 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 
