FOSSIL CYCADACEA. 151 
gens: in a young state they are coiled up like a crosier, as 
in ferns. 
The Cycadez have the general aspect of the Zamiz, but 
_ differ in their fructification and other characters ; and some 
_ species have the stem bifurcated towards the top, and attain 
a height of upwards of twenty feet ; for example, C. circinnalis. 
The stem in its internal structure* bears a close analogy 
to that of the Coniferz ; it has a central medullary column 
surrounded by a ligneous cylinder, divided by cellular 
medullary rays, each composed of bundles of vessels, and 
a thick cellular cortical investment or false bark,t com- 
posed of the persistent scales that formed the bases of the 
petioles. (See Pl. V. fig. 5.) 
The existing species of Cycadacez are exclusively natives 
of hot regions, and chiefly inhabit the West Indies, South 
Africa, Equinoctial America, Japan, New Holland, &e. ; 
not one species is known in Europe: a fact in striking con- 
trast with the abundance of fossil plants of this order, which 
occur throughout the secondary formations of England and 
the continent. +} 
No true cycads have hitherto been discovered in the car- 
boniferous deposits ; it is in the floras of the secondary 
epochs, from the new Red to the Cretaceous inclusive, that 
this tribe of plants forms an important feature. The foliage, 
stems, and fruits, occur in a fossil state; and as these organs 
cannot be referred with certainty to their respective plants, 
distinct genera are formed for their reception. 
Foliage.—From the tough and durable nature of the 
leaves, the foliage of the Cycadeze occurs in a fine state of 
* See Bd. pl. Ixii. 
+ See Bd. vol. i. pp. 494—498, for detailed description of structure 
in recent and fossil Zamize and Cycadez. 
+ The most interesting collection of living Cycadee and Zamiz 
near London, is that of James Yates, Esq., of Lauderdale House, 
Highgate ; it comprises choice examples of several of the sub-genera 
into which these plants are now divided by botanists. 
