224 
AMERICAN JOURNAL OF BOTANY 
[Vol. 8 
a single pair, of the mature cones about oppositely borne. The basal 
scales of the cones may be quite grown round by the bark. As the tree is 
destined to grow forward, there is of course nothing like an initial stage of 
true monocarpy in which apical growth must fail. 
Obviously in those species of Cycadeoidea such as C. dacotensis and 
C. Reichenbachiana, with a very heavy armor and scattering fruit axes, 
there may have been retention of the mature cones for several seasons, 
closely packed in between the leaf bases and there kept dry and free from 
decay by an abundant drooping ramentum. But the cones themselves did 
not tend to persist intact after maturity, because the Araucaria-like grouping 
of the sporophylls allowed easy separation and splitting free of seed stem 
and interseminal scale alike; while a simulated monocarpy does not suffi- 
ciently explain the condition found in the several cycadeoid species above 
cited. In order, however, to reach certain main conclusions it is necessary 
briefly to bring to view the xerophyllous character of the heavy-stemmed 
cycads, their geographic range, and also the climatic factor. 
Xerophyllous Features of the Cycadeoids 
Two main series of the petrified cycadeoid stems occur in the western 
Cretaceous. The lower series is from the Morrison (Como of Marsh). 
At one point near the so-called *'Bone Camp" in the Freeze Out Hills 
twenty miles northerly from Medicine Bow, Wyoming, the trunks have 
been found abundant in close association with the sauropod dinosaurs; 
but the cycad species again recur more scatteringly with the dinosaurs in 
the western Black Hills '*rim." The stems are so beset by scaly ramentum 
that resemblance to an ''old man cactus" was early suggested, as some 
evidence of growth in dry situations, although this idea is neither con- 
firmed nor contradicted by the presence of a fairly primitive pine (?) which 
I lately found closely associated with the cycads of the "Bone Camp" 
(so named from the bones of the great dinosaurs there found). The 
wood of these early pinaceans is dense, the wood rays are small, and the 
growth rings are very pronounced. Evidently growth was sharply seasonal, 
summer and winter, or dry and wet. 
The second and greater series of petrified trunks occurs in the succeeding 
Lakota of the Black Hills, with several hundred feet of sediments inter- 
vening. The horizon is considerably younger, and conifer stems are again 
conspicuously associated, though insufficiently studied. One is an Arau- 
carian, called by Knowlton Araucarioxylon Hoppertoniae. Again the 
growth rings are pronounced.^ 
^ This wood offers a simple but strong structure contrast to that found with the 
cycadeoids in the Freeze Outs, That wood is less Araucaroid, although the stems are 
above spoken of as early Pinaceans or Abietineans, in only a broad or perhaps Jeffreyan 
sense. I do not find full identity with any described form, though a relation to Prepinus 
(Hollick and Jeffrey) may be indicated by an imbedded shoot with centripetal wood. 
