Apr., 192 1 ] WIELAND MONOCARPY IN THE CYCADEOIDS 
225 
Whatever these conifers may mean, the cycads are in their entire or- 
ganization highly xerophyllous. There is, first, the profuse scaly ramentum 
thickly investing the frond bases as far out as preserved, and found scant in 
only a few instances (C. Stilwelli of the Black Hills, and an undescribed 
form from a much higher horizon in Alberta). Also, as Dr. Stopes has very 
lately found in a young lateral leaf crown long since cut at the British 
Museum, the under surfaces of the pinnules bear densely packed hairs. 
The feature is present in the American leaf series but varies greatly in its 
development with the species, of which at least four with well defined hairy 
leaves are known. The dense packing of pinnule hairs in Cycadeoidea 
ingens, as faintly preserved, simulates a tissue, in some parts of the frond 
as thick as the folded pinnules, and ending in a clear, sharp chalcedony line. 
These hairs are well cutinized, and the reduced transpiring surface, taken 
with the latitude (44°), suggests a warm- temperate desert climate. That 
these features and facts were long overlooked is quite inexcusable, though 
partly explained by the intention to come back to the critical study and illus- 
tration of cycadeoid frond structure. The character may be expected in 
some of the Mesozoic imprints, and is in physiologic accord with the free 
growth of angular scaly tomentum borne by the cycadeoid microsporophylls 
as they form the domelike apex of the young flower buds. 
The foliage crowns of five American species of cycadeoids are struc- 
turally known. These are in order of discovery: Cycadeoidea ingens, Cyca- 
della wyomingensis, Cycadeoidea colossalis, C. marshiana, and C. dartoni. 
But many more trunks with crowns remain to section. 
In general appearance the mature frond is absolutely determinate. The 
petiole was heavily clad in ramentum, varying considerably with the species, 
and becoming hairy instead of scaly about the insertion of the lowermost 
pinnules. Thence upward the upper surface of the rachis continues hairy 
with the hairy growth running out more or less freely all over the under 
surface of the pinnules; while the lower rachial surface and upper face of 
the pinnules remain smooth. (Note Plate XII, and text fig. i ; also Plate X, 
showing comparable Jurassic imprints.) 
The picture, therefore, of the heavy-stemmed cycadeoids is a very well 
defined one of dry desert plants with all their parts, stem, fronds, and fruits 
beset by scales, hairs, or tomentum. And, moreover, a curious but deeply 
interesting bit of confirmatory geologic evidence is afforded by the presence 
in the Lakota of reefs of calcareous tufa accompanied by numerous polished 
pebbles, held to mark recedent lake shores of increasingly dry regions. 
Though it would be an error to view the cycadeoids as dependent on as 
There are no resin canals, and no bars of Sanio or other modern features in either the 
tracheids or the rays. The radial tracheid pits are in one row, very rarely two, and never 
crowded or compressed. The rays are one to twenty cells high, normally ten, and one 
cell thick, — or two, for a distance of a cell or two. 
It is probable that both these types of wood, Araucaroid and Pinoid or more Abie- 
tinoid, will yet be found occurring alike in both of the cycadeoid horizons. 
