SPERMATOPHYTES 
185 
(2) BENNETTITALES 
General character. The members of this extinct group were very 
conspicuous during theMesozoic, and they have been called fossil cycads. 
In fact, the Mesozoic has been called the age of cycads, so far as plants 
are concerned. Recent investigations have shown, however, that the 
Bennettitales are very distinct from the living cycads. They were ex- 
traordinarily abundant during the Jurassic, numerous remains having 
been found in North America, Europe, and Asia, and extending into 
the arctic regions. The richest display of forms occurs in the United 
States (Maryland, South Dakota, and Wyoming), the conspicuous 
American genera being Cycadeoidea and Cycadella, and in Mexico. 
Sporophyte. The sporophyte body is generally tuberous in form, 
sometimes very large, but short columnar trunks (three to four meters 
high) also occur. This stem is 
covered by a heavy armor of 
leaf bases, among which there 
are wedged numerous short 
axillary branches, each bearing 
a terminal strobilus (fig. 426). 
The occurrence of numerous 
strobili on lateral branches is in 
striking contrast with the usually 
solitary terminal strobilus of the 
cycads. A second striking ex- 
ternal feature is the occurrence 
of an abundance of membranous 
scales (ramentuni), which are 
packed among the leaf bases 
and sometimes sheath the whole 
body with a feltlike mass. This FIG. 426. Photograph of fossil trunk of 
ramentum is characteristic of Cycadeoidea, showing the tuberous body and 
ferns, and is often conspicuous the armor of leaf bases, wedged among which 
r may be seen numerous strobui. Alter 
upon the trunks of tree ferns. WIELAND. 
The anatomy of the stem is 
exactly like that of the cycads ; with a very thick cortex, a compara- 
tively thin vascular cylinder, and a large pith. The vascular bundles 
composing the cylinder are collateral, with the protoxylem in contact 
with the pith (endarch). In the leaves, however, the protoxylem 
