368 WILLIS : MORPHOLOGY OF THE PODOS'PEMACEÆ 
extremely interesting illustration of how plastic the form of 
the plant may be when once it has got over the difficulties 
presented in most plants above the mosses by the presence 
of a more or less rigid skeletal tissue and by the absence of 
merismatic activity in all parts. Here the form is deter- 
mined before the bundles become stiffened in the flowering 
season, and the capacity for renewed merismatic activity 
possessed by nearly all the cells enables a great variety of 
form to be produced, chiefly by simple irregularities or 
difterences in the rate of growth of the different parts or 
cells. Almost incredible though it seems at first glance, the 
various forms in PI. XXV. and the left-hand part of PI. XXYI. 
are all forms of one plant, not eTen varietally distinct 
from one another, unless the large creeping form be distinct 
from the small creeping one. Detailed work on the spot 
with living plants is required to determine with certainty 
whether there is any heredity of the form of any individual, 
but so far as Mr. Barber’s observations go, and they confirm 
what I have mentioned above as occurring in Dicræa stylosa 
fucoides, the particular form of any individual seems 
mainly, if not entirely, in a direct correlation with the 
environment. Plants on the top of the rock, when crowded, 
tend apparently to the nearly symmetrical cup or disc form, 
and those on the sides of the rock to the form in which thie 
lower side is produced to a greater length than the upper, 
while when there is plenty of room the creeping form seems 
more common. This last form, however, seems quite absent 
in the Atgaon material. 
The secondary shoots are very closely similar to those of 
Dicræa, and some or all of them ultimately become flori- 
ferous, while the tissues leading to them become woody in 
the usual way. The bracts form just as in Dicræa, with 
broad sheathing bases and deciduous tips (PI. XXIV., flg. 8). 
The solitary terminal flower emerges from a spathe as usual, 
and stands erect ; it is anemophilous, as in all the other 
Indian forms. The general floral structure is like that of 
Podostemon, with a dorsiventral ovary which ripens to 
