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group which is now usually considered to be a separate phylum 
under the name of Cycadophyta, and no group, existing or fossil, 
has excited a greater theoretic interest in recent years. 
Pinnate fronds, like those of modern cveads, have been found 
as fossil impressions from the Carboniferous to the present, and 
the Mesozoic has often been spoken of as the Age of Cyecads. 
The assumption that this wealth of Mesozoic forms represented 
plants just like the existing Cycads has become entirely discredited, 
and the three genera restored constitute a significant part of the 
evidence for this change of opinion. 
The modern cyeads, of which many specimens are to be seen in 
the Conservatories (Tlouse No. 12), constitute a compact group of 
about one hundred species of the tropical and subtropical regions 
of both hemispheres. [very genus is at present represented in 
the Botanic Garden collection. These plants have columnar or 
tuberous stems, armored with old leaf-bases and crowned with 
whorls of graceful pinnate leaves. The pollen and ovules are pro- 
duced in separate and often large cones which are usually terminal 
at the center of the crown of leaves or sometimes in the axils of 
these leaves. Along with the Ginkgo, among modern seed plants, 
the sperm-cells are ciliated and swim from the pollen-chamber to 
the ege-cells, a habit which harks back to the aquatic ancestors of 
all land plants. Aithough the ancestors of the existing cycads are 
certainly pre-Tertiary in origin, they are now segregated in a 
sulk of their Mesozoic 
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ae 
separate order—the Cycadales, and the 
relatives are referred to two distinet orders—the Williamsoniales, 
to which JVielandielia and Wulliamsonia belong, and the Cycade- 
oidales, to which Cycadcoidea belongs. 
The Williamsoniales are a protean and long-lived group of 
forms, unfortunately known almost entirely from impressions. 
They appear in the late Paleozoic and continue sparingly into the 
early Tertiary. They have slender branched stems of considerable 
length and, instead of cones, a sort of a rude flower, consisting of 
a central conical mass of seeds and sterile scales, surrounded by a 
whorl of pollen-bearing appendages. 
The upper Triassic genus, H/ielandiclla, had an elongated slender 
stem not over an inch in diameter, with repeated dichotomies, pre- 
vailingly naked except in the region of the forks, where it bore 
