WorsdelL — The Structure and Origin of the Cycadaceae. 153 
in supplying the sporangia. The others, however, generally show some 
sign of it. It is highly interesting to find that the sterile sporophylls at 
the base of the cone contain bundles which, no longer compelled to 
submit to the above-named adaptive modification, revert back and tend 
to assume the concentric structure of the past (Fig. 17). 
The girdle-like character of the leaf-trace system in the stems of 
modern Cycads is a recently-adopted modification ; for in the Medulloseae 
and Lyginodendron, as also in the Bennettiteae, the leaf-traces pursue 
a directly radial course to the cylinder ; I noticed with much interest 
that this was also the case with the traces passing in from the cotyledons 
in a seedling of Cycas ; and the same thing is seen in the case of the 
sporophyll-traces of the cones. These four sets of facts prove that the 
radial course of the leaf-traces is the ancestral condition of affairs. 
As regards the morphology of the foliar organs and the mode of 
insertion of the sporangia : both foliage-leaves and sporophylls, in view 
of the Pteridospermic ancestry of the Cycads, must be regarded as organs 
which have become reduced in complexity of outline from the condition 
of the Fern-like foliar organs of the past. The decompound foliage-leaves 
of the Pteridosperms have become transformed into mere pinnately-divided 
organs in the modern forms 1 . In the former (e. g. in Lyginodendron and 
Neuropterideae) it would appear that both male and female sporangia were 
borne as terminal organs on ultimate subdivisions of a decompound 2 , dorsi- 
ventral foliar organ which was either assimilating or not. 
This terminal position of the reproductive organs I regard as an ancient 
primitive character, a reminiscence of the remote period when not only 
these ultimate ramifications of the sporophyll, but the entire organ itself, 
possessed radial symmetry 3 ; for I follow Celakovsky’s view that all foliar 
organs, including even such highly complex dorsiventral forms as the 
Fern-leaves, have sprung originally from the sympodially-grouped repro- 
ductions or repetitions of a bryophytic sporogonium. Traces of this 
primitive character may still be found in some of the recent Ferns, such as 
Hymenophyllaceae, Schizaeaceae, Cyatheaceae. 
In the group Bennettiteae the radial symmetry in the female sex is 
possessed by the entire sporophyll bearing the seed in a terminal position. 
Whether this c cone,’ considered in its entirety, is a reduced or a primitive 
structure we have, at present, no means of determining. On the male side 
the sporophyll appears to possess a dorsiventral structure with superficially- 
placed sporangia. In Cycadospadix the sporangia on the female side also 
seem to occupy a superficial position. 
1 Cycas Micholitzii, Dyer, recently imported from Annam, differs from all other known species 
of that genus in possessing repeatedly- dichotomizing pinnae, and hence probably represents a more 
ancient type of leaf than the ordinary simply pinnate form. 
2 Possibly some were of much simpler conformation. 
3 Cf. male and female sporophylls of Cordaiteae. 
