398 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1907, 
dendron. Anatomically it stands at a lower level than that genus, 
for its vascular cylinder is without a pith, constituting a protostele 
analogous to that occurring in most species of the recent Fern-genus 
Gleichenia. 
NEUROPTERIDEA., 
In the well-known species Veuropteris heterophylla (pl. 11), bodies 
of about the size and shape of a small hazelnut were found by Mr. 
Kidston, in material from the Middle Coal Measures, attached to a 
rachis bearing the characteristic pinnules (fig. 13). Unfortunately 
there is no preservation of structure in this case, but the external 
characters afford sufficient 
evidence of the seed nature 
of the organ. Beyond the 
fact that the seed was one of 
those with radial symmetry 
and that it had a fibrous 
envelope, there are no de- 
tails to record. The point 
of chief interest is the fact 
that these large seeds were 
borne on a frond so little 
modified as to show the or- 
dinary vegetative form of 
pinnule, another indication 
of the absence, in this group, 
of differentiated sporophylls. 
According to Mr. Kidston, 
the seeds fall under the 
genus Rhabdocarpus of 
Goppert and Berger. 
Fic. 13.—Neuropteris heterophylla. Seed, at- Mr. Kadston was thus the 
toned to, branch of te teohe bearing I9Pfiret to. observe) direct cof 
tinuity between the seed 
and the frond in a Fern-like Paleozoic plant. The family of the 
Neuropteridex, of which the plant in question is a representative, 
is well known from a structural point of view. As Renault dem- 
onstrated in 1883, the petrified petioles named J/yelovylon by 
Brongniart belonged to the fronds of Neuropteris and Alethopteris, 
while Weber showed that Myeloxylon petioles were borne on J/edul- 
losa stems. Thus we have a fairly complete knowledge of the anat- 
omy in certain members of the family. The stems of J/edullosa, as 
has long been known, have a complex structure, the vascular system 
being of the “ polystelic” type, with secondary formation of wood 
and bast around each stele. This structure finds its simplest ex- 
pression in the British species Medullosa anglica of Lower Coal- 
