F. W. Oliver. 
238 
Bothrodendron for this genus, known in Devonian rocks is among 
the most ancient of which the remains are preserved. This 
digression will serve as an illustration of the way in which the 
sporophylls of the Lycopod line have become involved and modified 
in connection with the cryptogamic phase in a manner finding its 
parallel in other evolutionary lines in the parts associated with the 
seeds themselves. 
The Cycadophyta. 
We turn now to the great series of the Cycadophyta, which 
formed such a predominant portion of the Mesozoic vegetation and 
of which our existing Cycads represent the surviving residuum. 
Between this series and the Pteridosperms the closest relation¬ 
ship is generally admitted to exist, a relationship which is reflected 
in the habit, vegetative anatomy and seed structure. In view of 
the many points of agreement, it is reasonable to suppose that the 
Cycadophyta .may have sprung from the Pteridosperms, though 
at present it is hardly possible to indicate the exact line or lines of 
descent. 
Within the limits of the Cycadophyta two well-marked 
families have been recognised : the Cycadeae and the Bennettiteae. 
The former of these is best represented by the surviving Cycads r 
the latter by Bennettites and the rich series of Cycadeoideas from 
the Jurassic rocks of N. America. It is probable, notwith¬ 
standing the unusually full information now available on the 
representatives of these two families, that our acquaintance with 
the range of variation presented by the Cycadophytes as a whole is 
very incomplete. 
Cycas itself affords what may be an interesting survival from 
the Pteridospermic stage in its unspecialised fern-like carpels, 
which, though produced in periodic rotation with the vegetative 
leaves, are borne on the main axis of the plant. Among other 
representatives of the group a more advanced condition is met 
with, both in the specialisation of the sporophylls and in their 
concentration upon special axes to form definite cones. On the 
whole the Cycads afford an example of an easily recognisable 
derivative of the Pteridosperm-plan in which a certain amount of 
concentration and specialisation has taken place. In this respect 
the group is somewhat on the level of organisation of a palaeozoic 
Lycopod, though, in the latter case, we are of course dealing with, 
plants of cryptogamic status. 
1 D. H. Scott, loc. cit., p. 171. 
