BOTANY: C. J. CHAMBERLAIN 
87 
true ferns; but, whether a given specimen should be assigned to the ferns 
or to these primitive seed plants, cannot be determined by the leaves 
alone. The only decisive character is the seed. 
From splendidly preserved material, Enghsh botanists have been 
making a vigorous study of this group, so that their results are avail- 
able for comparison. Their researches have covered the external form 
and also the internal structure of the stem, leaf, root, microsporangium 
and megasporangium; but, as yet, almost nothing is known about the 
gametophytes and embryo. 
A Mesozoic order — known as the Bennetti tales — which may have been 
the predecessor of the cycads, was also fern-Hke in appearance. These 
forms still retained the unbranched trunk and crown of pinnate leaves, 
so characteristic of ferns and Paleozoic seed plants; but only pinnae 
of the simplest type persisted and the trunk was short and stocky, so 
that in general appearance they bore more resemblance to the modern 
cycads than to their Paleozoic ancestors. The microsporangia were 
borne on a whorl of leaves, reduced considerably, but still retaining the 
pinnate character of the foliage leaves. The seed bearing structures, 
however, were collected into a compact cone, in which no one but a 
morphologist would recognize the homologues of leaves. Both the pollen 
producing and the ovule bearing leaves were in the same strobilus, so 
that the bisporangiate strobilus is a striking feature of the group, or at 
least, of its upper Mesozoic members. These strobili were small and 
numerous and were borne in the axils of foliage leaves. The material 
which has been under investigation has come from Idaho, Dakota, 
Maryland, Mexico, Europe and India; but this does not mean that 
the group was confined to the northern hemisphere, for these places 
are all in the university belt or are easily reached from universities. 
Forms which may belong here, or may belong to the true cycads, occur 
in Cretaceous deposits in South Africa, and vast regions remain to be 
explored. 
G. R. Wieland has made the most extensive contributions in this 
field, but, as in case of the Paleozoic members of the phylum, scarcely 
anything is known of the gametophytes and not much is known about 
even the sporophyte structures of Triassic forms. 
While I have studied, with great interest, the best material of the 
Paleozoic and Mesozoic forms, my own research has been confined to 
the only living family of the phylum, the Cycadaceae, or cycads. 
The geological history of the cycads is still very indefinite, largely 
because stem and leaf characters are hardly sufficient to distinguish 
true cycads from the Mesozoic Bennettitales. The confident determina- 
