34 Bower,— Studies in the Phytogeny of the Filicales. VI. 
Phlebodium , Phymatodes , Niphobolus , Drynaria , and also N eocheiropteris , 
represent the modern derivatives of the phylum of the Dipteridinae. 
According to the spread of the sori, and their flowing together to form 
extensive soral areas, these derivatives would be ranked as Polypodioid 
or Acrostichoid. There is no reason to assume that any limit should exist 
between these types, and the general similarity of their habit supports their 
near relation. 
Photinopteris and Dryostachya are clearly referable as Acrostichoid 
derivatives from Drynaria} The stelar structure (Text-fig. 11) accords 
with this, though not distinctive evidence, and for Drynaria itself the 
Dipterid affinity may be suggested with as much force as for Phlebodium or 
Phymatodes . 
The case for a Dipterid relation of Cheiropleuria has already been 
argued at length in a previous memoir of this series, 1 2 and the conclusion 
was drawn (p. 524) that it is a Fern of Matonioid-Dipterid affinity, which has, 
however, retained its primitive dermal hairs, and the protostelic structure 
resembling that of the still more archaic Gleicheniaceae, while it had 
adopted a type of leaf and of sorus essentially resembling the relatively 
advanced species of Dipteris, but carried to a still more advanced state ; for 
the sorus is mixed and Acrostichoid, with initiation of a diplodesmic 
structure of the fertile areas. 
In the same memoir the position of Platy cerium was also discussed. It 
was concluded that it also is a Dipterid derivative, specialized for an 
epiphytic habit. This conclusion may be further tested in view of data 
since come to hand. A memoir by Heinrich Ritter von Straszewski has 
dealt with ‘ Die Farngattung Platycerium \ 3 He describes its prothallus, 
noting especially the multicellular glandular hairs on its under surface, com- 
parable with those of the Cyatheaceae and Diacalpe. The antheridia have 
a divided cap-cell. In writing on the vascular structure he does not seem 
to have been aware of the work of Miss Allison. 4 His observations on 
P. stemaria (Beauv.), Desv. (= P. Aethiopicum, Hk.), correspond to hers 
in showing a medullary system within an outer ring of meristeles and 
a much-divided leaf-trace. But he is in error when he attempts to correct 
the observations of Hofmeister on P. alcicorne by the suggestion that he had 
worked on young material. As Miss Allison has shown on quite mature 
stems, the meristeles are disposed in a single circle in that species. He 
notes that lateral buds spring from the axis below the leaf-insertions, 
an arrangement which has its counterpart in many Ferns of Cyatheoid 
affinity. He advances reasons for the belief that the humus leaf was phyleti- 
cally prior to the sporophyll type, and that Platycerium originally had only 
1 Compare Diels, 1 . c., p. 328 ; Christ, 1 . c., pp. 117, 121 ; Frau Schumann, 1 . c., p. 245. 
2 No. V, Ann. of Bot., vol. xxix, p. 495. 3 Flora, 1915, p. 271, &e. 
4 New Phytologist, vol. xii, 1913, p. 31 1. 
