8 
Birbal Sahni. 
xylem, with the internal phloem of the main stele. 
The branch stele in Adiantum trapeziforme , which has a 
dictyostelic adult stem, is at its base a completely closed tube, 
having its pith continuous with that of the main axis (Gwynne- 
Vaughan, loc. cit., p. 724). In some of the Cyatheaj we meet with 
a similar condition, which may be somewhat complicated by the 
presence of a medullary system of strands, both in the main axis 
and in the branch. The branch may either develop its medullary 
system independently of that in the main axis, or the two may be 
continuous through the gap at the base of the branch. The latter 
condition is described by Stenzel in a Fern erroneously called by 
him Diplaziumgiganteum. 1 In Hemitelia setosa (Klf.) Mett. Professor 
Bower records a branching stolon—the main stolon corresponded 
with the mother axis in its advanced type of Cyatheoid structure, 
while the secondary stolon was solenostelic, though it still possessed 
a weak medullary system. 
In some material of a Malayan species of Drymoglossum, for 
which I am indebted to Mr. F. T. Brooks, the branch possessed 
at its base a C-shaped strand with its gap adaxial. This strand 
almost immediately broke up into two, which divided further so as 
to form a reticulate stele exactly like that in the main axis. 
Lastly, we may mention the comprehensive genus Poly podium 
among a large number of other Ferns with highly dissected steles 
and creeping rhizomes. In a great many of these the branch at its 
very base is dictyostelic, and in external appearance does not differ 
from the main axis, except perhaps in size. Thus Klein 2 describes 
in Poly podium Heracleum side branches which are attached to the 
main axis by a narrow base; the dictyostele in such branches is 
correspondingly contracted at its insertion on that of the main axis, 
and the first one or more leaves of the branch may fail to attain 
their normal stature. In P. quercifolium the same author describes 
both branches growing out from a contracted base and possessing 
a miniature dictyostele which increases in diameter with the branch 
itself; and others which are from the very start identical in structure 
with the main axis. These latter cases are not far removed from 
dichotomy in the wider sense. Here we may refer also to the 
Osmundacete, in which dichotomy of the rhizome has been described 
1 The genus Diplazium is generally placed in the proximity of Asplenium 
and S colopendrium, but the description of the stem and petiole of Stenzel’s Fern 
points unmistakeably towards the typical Cyatheaceous structure. 
2 Klein, L., Nova Acta Leop.-Carol. Deutschen Akad. d. Naturf., Bd. XL1I 
No. 7, p. 335 ff., 1881. 
