138 
of cycads, the nervation is pinnate, that is, consisting of a 
median nerve or midrib, with minor nerves or veins extending 
from the aideb to the monk in a manner similar to that of 
most of the ferns with which we are familiar (Fig. A); and it 
is of inter note that, based on the leaf characters alone, 
extend from base to are es B), or (in Cycas) only a single 
median nerve or midrib (Fig. C.). 
ycads, regarded as a ne or natural family of plants, 
evidently represent a waning type of vegetation in the existing 
flora of the Earth. This is indicated not only by their relative 
specie 
of specific and ae forms, and were practically world-wide 
in their Rea 
About thirty- re genera, including about 280 species, based 
n. 
s, or the flowers 
constantly brought to light. They had their ae as a distinct 
Oo 
the latter were a attached to stems or trunks of cyca- 
deoid structure. 
