f 
DISTRIBUTION AND RELATIONSHIPS OF THE 
CYCADEOIDSi 
G. R. WiELAND 
I. Distribution 
Plant geography is an impressive subject. It should find extension in 
time. Hitherto, little more than the fossil plant localities have been 
indicated. But the larger outlines of the Mesozoic forests must yet appear. 
The characteristic forms are slowly being determined; and sufficient pro- 
gress has been made in paleogeography to permit initial hypothetic mapping 
of some of the forests. That even this rougher mapping discloses new facts 
is certain. With the old continental boundaries in view it becomes logical 
to ask why the Rhaetic plants of the Virginia-North Carolina coal field are 
so megaphyllous, while those of the southern Andine region are very micro- 
phyllous. Does not a larger part of the Jurassic Ginkgo record also indicate 
wide climatic variation, second only in extent to that of the time of the 
Glossopteris flora? Would it not be singular if plant evidence remained 
whol y at variance from that of the insects and invertebrates, indicating 
climatic cooling in the late Trias and early Jura, not local in character? 
When one-sided evidence is once recognized as such, it becomes less 
misleading. The picture of the typical Mesozoic forest with a tropic sun 
beating on its xerophylls has been too grandly simple. A remnant of the 
equisetes, ferns, Araucarias, cycads, the pines, and the Ginkgos! Think 
this over. No real forests except coniferous ''pure stands" from the close 
of the Perm'an to the Comanchean angiosperms? Unbelievable. The 
evidence already carries us much further, and the fact is being slowly dis- 
closed that varied forests of microphyllous cycadeoids must have had a 
greater area than all other gymnospermous forests put together, all through 
Triassic and Jurassic time. 
The record is not scanty, as I know from the field. There has been no 
reason for the view that the fossil cycads are simply the underbrush of 
tropical forests, or were merely columnar-stemmed fringing types like the 
palmetto. Yet this has been the only view. Nathorst, indeed, left open 
the question of the habitus of Wielandiella; but Jeffrey thought this form 
was procumbent. Williamsoniella (see fig. i) would look less so. There is, 
however, no evidence for procumbency in either case. On the contrary, 
the branching in both these small-stemmed cycadeoids is but little simpler 
than that of some magnolias, and it is easier far to look upon them as shrubs, 
1 Invitation address read before the joint session of Section G, A. A. A. S., the Botanical 
Society of America, and the American Phytopathological Society, in the symposium on the 
" Phylogeny of Seed Plants," at St. Louis, December 30, 1919. 
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