The Anatomy of Nephrolepis volubilis J.Sm. 271 
the anatomy of the mother-plant are necessary than are at present 
available. 
The foregoing sketch of the range in habit and structure 
exhibited by the species of Nephrolepis may perhaps justify the follow¬ 
ing view regarding their relative positions within the genus. That 
a well-marked tendency towards the epiphytic habit is exhibited by 
most of the species of the genus is abundantly clear from what has 
preceded. Starting from a hypothetical solenostelic form with a 
short erect stock bearing leaves with simple leaf-traces, the 
epiphytic tendency may be considered to have found expression in 
two ways, and to have led to the gradual evolution of two main 
types of habit. On the one hand, the stem itself became a scandent 
rhizome bearing distant leaves, and forms like N. ramosa and 
N. altescandens were evolved. On the other hand, a much more 
specialized and highly efficient organ, the stolon (which is probably 
to be taken as a highly modified branch of the stem) was evolved 
for the purpose, with conspicuously successful results ( N . volubilis , 
N. cordifolia). 
The leaf-trace, along each of these two lines of progress, 
followed a course of elaboration of its own, from the simple 
(iV. ramosa ) to the compound (N. altescandens ), along the first of 
these lines. Sufficient data are not available to enable one to 
delineate accurately the course of elaboration through which the 
leaf-trace passed in the stoloniferous forms. However, there is an 
indication (a faint one it must be admitted) that the evolution of 
the leaf-trace was less gradual in this series, for in N. cordifolia the 
simple arc-like trace described by Chandler 1 in one of the earlier- 
formed leaves of the sporeling soon gives place first to a double 
and then to a triple trace in the later leaves. 
In this relation a detailed study of the sporelings of different 
species of Nephrolepis , on the lines of Chandler’s work, would 
probably throw considerable light on the question. That a study 
of the lateral plants, (which are more easily obtainable) will not 
enlighten us to any great extent on this point is evident from the 
fact that, the lateral plant which, as already stated on p. 253, is 
produced under conditions favourable to rapid growth, no longer 
exhibits the earlier stages in the evolution of the leaf-trace. 
If the conjecture put forward on the page just referred to has 
any justification, we have before us a remarkable case where 
exceptionally favourable physiological conditions are potent to the 
1 Chandler, l.c., p. 391 
