4 ERNST ANTEVS, SOME MESOZOIC PLANTS. 
pinna, become more and more confluent. The lowest basal pinnules are inserted in 
the angle between the rachis and the pinna, so that they are provided with veins 
from each of them. In this respect, however, there is a rather great variation among 
FEISTMANTEL”S specimens. In the latter the pinnules sometimes do not run down 
along the main rachis at all, whereas, in other cases there are similar pinnules on 
the rachis between two pinnae. There is no midrib, but the veins arise from the 
rachis. They are forked, fine, very close, and radiate towards the distal as well as 
towards the proximal margin of the pinnule. According to FEISTMANTEL the greater 
number of the not very numerous veins originate in a common point at the base of 
the leaflet and radiate with repeated bifurcation. It cannot be decided whether it 
is the same with the present specimens; but there seems to be a variation according 
to the shape of the pinnules. 
Owing to the resisting power of their thick leaves, the fossils are very well pre- 
served, and not only the external morphology but also the structure of the cuticle 
can be studied after the usual treatment. Though the veins can be discerned very 
distinetly in the impressions, they are not at all distinguished by any difference of 
the epidermis. The thick cuticle is similar on both sides of the leaf. TIt is of rather 
large, isodiametrically polygonal cells with not very thick walls. They have each a 
distinct papilla. Such papillae are missing in the examined forms of Thinnfeldia 
ETTINGSH., a closely allied genus, which, as to the epidermis, otherwise presents a 
great resemblance to the plant in question. Nor do GoTHAN or SEWARD mention 
any similar papillae in Dicroidium odontopteroides GoTHAN from South Africa. 
The numerous stomata are equally distributed over the whole surface of the leaf 
and occur in about the same number on both sides of it. They are surrounded by 
4—7 »Wallzellen»>, whose outer walls form a thickened circle. The inner walls as well 
as the radial ones are, on the contrary, thin and lie a little immersed. The guard- 
ian cells are not preserved. Accordingly the stomata agree perfectly with those 
of Thinnfeldia. 
The fact that the papillae which according to HABERLANDT!' are to be considered 
as organs of light-perception occur on both sides, combined with the structure of 
the cuticle for the rest, may show that the frond has had a vertical position by 
means of which both sides have been subjected to the effect of the sun in the same 
degree. 
As characteristics of the new genus Dicroidium, GoTHAN mentions among other 
things: »Epidermis zart. Zellwände der Epidermis deutlich unduliert, zart. Spaltöff- 
nungen ohne ”Wallzellen”. Spaltöffnungen unregelmässig verteilt> (1912, p. 78). 
He has, however, only examined Dicroidium odontopteroides GoTHAN from South Africa 
and supposes that D. Feistmanteli agrees with this plant, which is not the case. No 
doubt, it would be better to exclude the structure of cutiecle from the diagnosis un- 
til different forms of Dicroidium and Thinnfeldia have been examined in this respect; 
for there may be sufficiently great and numerous differences, all the same, for a 
separation of the two genera. Moreover, we should not lay too much stress upon 
! HABERLANDT. Die Lichtsinnesorgane der Laubblätter. Leipzig 1905. 
