206 The Palaeontological Record. II. Plants 
leaves give the Cycads a superficial resemblance in habit to Palms, 
Recent Cycads are dioecious; throughout the family the male fructifi- 
cation is in the form of a cone, each scale of the cone representing 
a stamen, and bearing on its lower surface numerous pollen-sacs, 
grouped in sori like the sporangia of Ferns. In all the genera, except 
Cycas itself, the female fructifications are likewise cones, each carpel 
bearing two ovules on its margin. In Cycas, however, no female 
cone is produced, but the leaf-like carpels, bearing from two to six 
ovules each, are borne directly on the main stem of the plant in 
rosettes alternating with those of the ordinary leaves—the most 
primitive arrangement known in any living seed-plant. The whole 
Order is relatively primitive, as shown most strikingly in its crypto- 
gamic mode of fertilisation, by means of spermatozoids, which it shares 
with the maidenhair tree alone, among recent seed-plants. 
In all the older Mesozoic rocks, from the Trias to the Lower 
Cretaceous, plants of the Cycad class (Cycadophyta, to use Nathorst’s 
comprehensive name) are extraordinarily abundant in all parts of the 
world; in fact they were almost as prominent in the flora of those 
ages as the Dicotyledons are in that of our own day. In habit 
and to a great extent in anatomy, the Mesozoic Cycadophyta for the 
most part much resemble the recent Cycadaceae. But, strange to 
say, it is only in the raress cases that the fructification has proved 
to be of the simple type characteristic of the recent family; the vast 
majority of the abundant fertile specimens yielded by the Mesozoic 
rocks possess a type of reproductive apparatus far more elaborate 
than anything known in Cycadaceae or other Gymnosperms. The 
predominant Mesozoic family, characterised by this advanced repro- 
ductive organisation, is known as the Bennettiteae; in habit these 
plants resembled the more stunted Cycads of the recent flora, but 
differed from them in the presence of numerous lateral fructifi- 
cations, like large buds, borne on the stem among the crowded bases 
of the leaves. The organisation of these fructifications was first 
worked out on European specimens by Carruthers, Solms-Laubach, 
Lignier and others, but these observers had only more or less ripe 
fruits to deal with; the complete structure of the flower has only 
been elucidated within the last few years by the researches of 
Wieland on the magnificent American material, derived from the 
Upper Jurassic and Lower Cretaceous beds of Maryland, Dakota and 
Wyoming’. The word “flower” is used deliberately, for reasons 
which will be apparent from the following brief description, based 
on Wieland’s observations. 
The fructification is attached to the stem by a thick stalk, 
which, in its upper part, bears a large number of spirally arranged 
1G, R. Wieland, American Fossil Cycads, Carnegie Institution, Washington, 1906. 
