272 
Birbal Sahni. 
extent of eliminating from the ontogeny of a plant morphological 
features which probably marked important stages in its phylo¬ 
genetic history. 
From a study of the anatomy of N. ramosa we concluded on 
p. 266 that, in respect of the great similarity of structure 
respectively in the rhizome, branch, and the leaf at its origin, that 
plant formed a rather striking parallel to the case of the Hymeno- 
phyllaceae. Although N. ramosa belongs to a phyletically much 
higher group of ferns, the above-mentioned feature in its anatomy 
may possibly go in support of the view, so strikingly borne out by 
the vascular structure in the Hymenophyllaceae, that the strands of 
the stem and of the leaf are primitively identical structures. 1 
Finally, the extensive development of protostelic structure 
exhibited by the stolons of Nephrolepis cannot pass unnoticed. 
The main axis of the plant has acquired extraordinary powers of 
branching, and into its branches a large portion of its energies is 
diverted. It seems unreasonable to regard the stolon, possessing 
as it does such a primitive vascular organisation, as an indication 
of primitiveness of the genus. Much more likely seems the view 
that it is a highly specialized organ whose structure may in some 
way be connected with the conducting functions imposed upon it. 
In conclusion, I wish to express my thanks to Mr. Brooks not 
only for handing me the material of N. volubilis used in this 
research, but also for much help throughout the progress of the 
work. I have also to thank Mr. Boodle for valuable suggestions, 
and Professor Seward and Mr. Tansley for their kind interest in 
this investigation. I am also much indebted to Professor Seward 
for revising the manuscript. 
VII. Summary. 
Nephrolepis volubilis , J.Sm., a highly specialized member of 
the genus, is described. The stolons arising directly on the mother- 
plant (primary stolons) are smooth cylindrical organs (natural size 
photograph, Text-fig. 2) which scale forest trees up to 16 metres 
and enable lateral plants, borne on them at intervals, to reach 
heights far above the mother-plant which is rooted in the soil. 
Two to four shorter stolons which are wiry and irregularly 
coiled appear on each lateral plant, and seem to be contact-sensitive. 
They are climbing organs. 
1 Tansley, New Phytologist, 1907, p. 115. 
