236 
F. W. Oliver. 
day by the relatively conspicuous part which annuals play in desert 
floras. 1 
Additional characters, such as the resting embryo, may have 
been acquired later, for embryos have not been found in Palaeozoic 
seeds. In time also, with the assumption of some of its functions 
by other structures, the seed evidently underwent considerable 
simplification. 
Another consequence that followed in the wake of the seed- 
habit was the impetus given to advancement, as is well illustrated 
by the Mesozoic Cycadophyta to be referred to below. 
If reference be made to the chart (fig. 32), it will be noticed 
that the Filicineae are represented as a continuous strip of even 
width. At present, whilst our notions respecting this series are 
recovering but slowly from the rude shock dealt by the far-reaching 
nature of the pteridospermic encroachment, it seems hardly 
possible to attempt anything more definite. From a recent 
authoritative statement of the position it seems evident that, 
although true Cryptogamic Ferns existed in Palaeozoic times, some 
time must elapse before it will be possible to speak with confidence 
of their nature and extent. 2 
Vascular Cryptogams and the Seed-Habit. 
Before leaving the more primitive representatives of the 
Pteropsida-phylum some reference may be made to a feature in 
which they contrast in marked degree with the Lycopsida, viz., the 
lack of concentration and differentiation of their sporophylls. On 
the whole, the evidence goes to shew that in these megaphyllous 
forms we have to deal with relatively generalised and primitive 
types in which the form and aggregation of the sporophylls shew 
little specialisation in connection with the sporangium- or seed¬ 
bearing function. 
In the case of the Lycopsida the sporophylls are characteristically 
massed into cones, and shew an evident relation both in form and 
extent to spore production. 
In addition therefore to the more obvious differences in structure 
which form the basis on which Pteropsida and Lycopsida are dis¬ 
criminated, there seems to be some grounds for regarding the two 
1 Thus Schweinfurth, in W. P. May’s “ Helvvanand the Egyptian 
Desert,” enumerates 191 species as constituting the desert 
flora of H el wan, of which 116, i.e., 60°/ o are given as annuals. 
3 D. H. Scott, in Lotsy’s Progressus Rei Botanicae, Vol. I., 
pp. 177-189. 
