DISTRIBUTION AND RELATIONSHIPS OF THE CYCADEOIDS 1 65 
lithus, possibly known. Some of the foliage no doubt falls near or within 
the MeduUosans. But other forms may be added. Of such the lax cone 
Beania with two-seeded megasporophylls denotes variation toward the 
cycadeoids, so distinctly contemporaneous in the Trias-Jura transition 
or Rhaetic time. Here also I would mention the two remarkable Y- 
branched frond types known as Dicroidium and Thinnfeldia, both recently 
shown by Anteys to be xerophytic. They have been referred at one time 
or another to several gymnosperm groups, but not hitherto to the Ginkgos. 
In any case the fernlike aspect relates these frond genera on the seed-fern 
side. Nor do they appear remote from that somewhat more cycadeoid 
leaf type called Ptilozamites. This genus and the palpably ginkgoid and 
varied Baiera foliage, occur in well marked association in the Rhaetic of 
the southern hemisphere. No one who studies the Rhaetic and the succeed- 
ing Liassic or lower Jurassic plants in the field will ever again rest under any 
doubt about a steady and well marked transition from seed fern foliage 
toward cycadeoid and ginkgoid foliage. With this point emphasized it 
may be permissible to omit closer reference to structure, and to ask atten- 
tion to a cycadeoid relationship of a more recondite character because of a 
certain lack in the accumulation of fossil evidence, namely that to Araucaria. 
Araucaria 
That the araucarians attained specialization early, with retention of 
much primitiveness of feature, and that they are a discrete line coming down 
from the old cycadofilicalean complex, is indicated by analogy to the cyca- 
deoids. It is now evident that Araucaria has more in common with cycads 
and cycadeoids than was earlier supposed. The robust armored stem is 
analogous to that of the cycadeoids, this being true of structure, of cortical 
development, and of both the primary and the secondary branching. The 
roots freely send up young plants, and the seedlings are stout, cycad-like, 
and remarkably tenacious of life. Renewed growth of the reproductive 
shoot from a lateral bud is cycadaceous and cycadeoid, comparison being 
made with Wielandiella and Williamsonia scotica. The large pith and thin 
woody cylinder of the shoots, vegetative and reproductive, and the complete 
transition from foliage to fertile scales of the large cones are also cycad-like, 
as well as still more decidedly cycadeoid. The megasporophyll with its 
small ligule finds a counterpart in the decurved microsporophyll of the 
cycadeoids, and is aplosporophyllous, with the seed imbedded. 
Nor is it necessary to regard the araucarian seed-cone as greatly different 
from that of Cycadeoidea merely because the seed is decurved like that of 
cycads, instead of erect. In reality the fertile sporophyll is surrounded by 
infertile members almost identically as in Cycadeoidea. This significant 
comparison has been hitherto overlooked. Moreover the araucarian micro- 
sporophyll is also decurved and at the same time sends up an acuminate 
scale-tip which may well be regarded as the analogue of the spur seen in the 
