Juty 5, 1918] 
cating stems and Nilssonioid foliage proved 
the form of greatest interest; although very 
recently another related form, Williamsoniella, 
of quite equal interest from the Yorkshire 
coast has been reconstituted by Thomas. This 
has a very small perfect flower with somewhat 
seale-like microsporophylls, bearing, as it 
turns out, only a few pairs of sessile synangia. 
The stems are slender, and the foliage defi- 
nitely Nilssonian to Tzniopterid This rela- 
tionship was in Wéielandiella somewhat ob- 
secured by a peculiar prolongation of the mid- 
rib. 
Now this definite inclusion of Nilssonians 
amongst the small-flowered cyeadeoids demon- 
strates the presence of a great alliance related 
to the primitive magnolias and abundantly 
represented in the leafy records of the Meso- 
zoic. For it is seen that to this group must be 
added not only Teniopteris but Macroteni- 
opteris at least in part. In 1905 I called at- 
tention to these foliar types in Monograph 
XLVIII. of the U. S. Geol. Sur. in the follow- 
ing justifiable terms: 
The genera Nilssonia, Teniopteris and Oleandri- 
dium have now come to comprise numerous species 
of a very generalized and cosmopolitan type of 
leaf. As a consequence, it has become difficult, as 
always in such a case, to say definitely, in the ab- 
sence of extended revision, where the one genus 
ends and the other begins. Nevertheless we have 
every reason to believe that at the one end of the 
series there are characteristic ferns analogous to 
such living forms as Oleandra and Acrostichum, 
as well as marattiaceous forms, and at the other 
an important list of cyeadaceous forms. The 
closely related genera Pterophyllum and Anomo- 
zamites [now Wielandiella, in part] may be cited 
here. Anomozamites minor (Brongn.) Nath., as 
restored by Nathorst from specimens from the 
Rhitie of Scania, with its Williamsonia-like fruc- 
tifications, Nilssonia-like foliage, and branching 
habit, is especially to be mentioned in this connec- 
tion as one of the most interesting fossil plants 
known. This series is at the same time an exceed- 
ingly important one, eovering as it does a period 
extending over much of the Paleozoic to the close 
of the Jurassic at least, a period so fertile in the 
evolution of higher forms. 
From the Carboniferous to the Cretaceous 
there is, then, a great and cosmopolitan cy- 
SCIENCE 19 
eadeoid group with simple sparsely inserted 
leaves. This group is especially in evidence 
in the Rhitic, a period of marked change in 
the Mesozoic plant alignment. In the Northern 
hemisphere the Rhitic is generally notable for 
megaphyllous forms, especially so in the Rich- 
mond and North Carolina coal fields; but, as 
I found on the eastern side of the Andes in 
finely stratified Rhitic shales of Argentina, 
there are many small leafed and even scrub or 
upland forms. The small extent to which 
these forms showed netted venation is of 
course the weakest link in the chain of eyi- 
dence for dicotyl derivation. But it may be 
recalled that the presence of net-veined forms 
[Dictyozamites] is not an inference; while the 
perfunctory reference of the numerous net- 
veined leaves of the Mesozoic to ferns, rarely 
found fertile, rests on no sound or certain 
basis. The great lyrate ferns of the Rhiitic, 
Clathropteris and Dictyophyllum, are an ex- 
ception; also an adumbration of the higher 
net-veined types soon to become dominant. 
This subject has been considered more at 
length in a paper in the American Journal of 
Science (November, 1914). It is there sug- 
gested that polar stocks of unknown record 
may account in part for the seeming gap in 
the dicotyl leaf series. Also it should be noted 
that plastic, potent upland stocks (Bailey and 
Sinnott), are in the strictest sense of the word 
corollary to the main theory of radiation of 
animals and plants from the polar areas (Dar- 
win, Forbes, Riitimeyer, Saporta, Joseph Dal- 
ton Hooker, Asa Gray in the Dubuque Address 
of 1875, Narthorst, Wallace, Scribner, Wort- 
man, Wieland and Matthew). In any case the 
negative evidence indicates small flowers for 
the early dicotyls from the Permian on, and 
these are only likely to occur in some favored 
or unusual locality. 
It has been said that the resemblances be- 
tween Oycadeoid and dicotyl wood structure 
are deceptive, that some Magnolias (and the 
Trochodendrons) have lost their vessels, and 
that scalariform sculpture of the dicotyledonous 
vessel results from the lateral fusion of circu- 
lar pits (Jeffrey). Even if the first of these 
contentions, improbable as this now seems, 
