BERRY: FERN GENUS CLATHROPTERIS 285 
proaching 90 degrees, stout parallel secondaries. These usually 
alternate but not invariably. They proceed outward in almost 
straight courses nearly to the margin where they curve conspic- 
uously upward, becoming rapidly much reduced in size and ter- 
minate at the tips of the marginal teeth. The secondaries are 
connected at approximately regular intervals by relatively stout 
straight percurrent tertiaries at nearly right angles to the second- 
aries, and subordinate divisions result in an ultimately fine rec- 
tangular areolation with blind endings. 
This rectangular venation is rather consistently more regular 
than in the allied fossil genera and rather different from that of 
the existing Dipteriaceae. It is, however, approached very closely 
by certain existing Polypodiaceae with the so-called Drynaria 
composita type of venation. Among modern ferns that have a 
comparable venation might be mentioned various oriental species 
of Polypodiaceae, belonging to the genera Lomariopsis, Dryostach- 
yum, Polybotrya and Drynaria. The latter genus is especially 
like Clathropteris in the form of its pinnules, in their venation and 
(in some of its species) in their toothed margins. Drynaria 
comprises about a dozen species of epiphytes of the oriental tropics 
and the species Drynaria quercifolia is particularly like Clathrop- 
teris in respect to the characters just enumerated, although the 
general habit is very different. 
Although Schenk refers the fossil forms to the family Dictyop- 
terideae, the venation characters, more readily ascertainable from 
fragmentary specimens, which are the kind usually collected, have 
resulted in the usual reference of the fossils to the Polypodiaceae 
or Acrostichaceae, as is done by Ettingshausen, although it is 
obvious that they constitute a unique and distinct line of forms 
ancestral to the modern family Dipteriaceae. 
JoHNs HopKINS UNIVERSITY, 
BALTIMORE 
