266 
Birbal Sahtii. 
able distances apart). In the figure referred to, the two leaf- 
strands are still just attached to the ends of the cauline strands on 
the one side, while on the other the arc-like branch-trace is 
constituted by the attenuated portion of the xylem-ring. 1 
From the foregoing account of the species of Nephrolepis three 
interesting facts emerge. Firstly, an evident tendency in the genus 
for the products of branching of the stolon to remain adnate to one 
another for shorter or longer distances, so that their respective 
vascular strands lie more or less parallel to each other and enclosed 
within a common cortical envelope, before they finally become free. 
Secondly, the great uniformity in structure and mode of branching 
of the stolons in the different species, even when their habits are 
divergent. Thirdly, the great similarity of structure, in N. ramosa 
Moore, between the basal part of the leaf, and the stem on which it 
arises, and the exactly similar way in which the leaf- and branch- 
traces respectively originate. In this respect N. ramosa agrees 
with Trichomanes radicans and other members of the Hymeno- 
phyllacese. 
It may also be mentioned here that in the two closely allied 
species N. ramosa and N. altescandens, we see the transition from 
the simple arc-like leaf-trace of the former to the more advanced 
double trace of the latter. 1 
V. Biological Observations. 
There is abundant literature dealing with the biological aspects 
of Nephrolepis centred especially on the tubers and the stolons. 
Three of the most recent papers, two by Sperlich, 1 one by 
Heinricher, 3 contain a series of highly interesting observations on 
the growth and development of the tubers and stolons, studied by 
the latter author under artificial conditions of culture. Of these 
results the most remarkable appears to be Heinricher’s exposition 
of the great plasticity of the stolons which, moreover, can be 
controlled by the cultivator. For instance, by merely covering the 
rhizome over with earth he was able to transform it into a stolon 
which bore leaves directly , and possessed a single axial strand. 4 
' It must here be stated that the above account of N. ramosa and N. alte¬ 
scandens is based on a limited amount of dried material. 
3 Sperlich, Flora, 1906, p. 451 ; Flora, 1908, p. 341. 
* Heinricher, Flora, 1907, p. 43. 
* l.c., p. 63. See also pp. 57, 72. 
