1919.] The Sixth Indian Science Congress. cliii 
series of forms as regards their differentiation from the oldest 
rocks to the present day our task would be quite simple. We 
have, however, no record of such a complete series. There is 
no doubt that in a general way we have the strongest possible 
evidence of evolution from art but many stages in the 
series are missing, and, what is more, we have not. reached the 
beginning of the series vet. Among the plants known from the 
most ancient rocks a large number show a comparatively high 
grade of differentiation, far higher than that of the Liverworts, 
and we have no data as to what kind of plants which preceded 
them gave rise to them. As regards the fossil history of the 
Liverworts themselves I cannot do better than quote Dr. Scott. 
He says :-—“‘ The Palaeozoic records of this class of plants to 
which some botanists have assigned so important a place in the 
evolution of the Vegetable Kingdom are both scanty and 
doubtful. Inthe absence of any evidence as to reproductive 
organs or anatomical structure, it cannot be said that the pre- 
sence either of the Hepaticae or of the true Mosses in the 
Palaeozoic rocks has yet been demonstrated. It is 
that no trace of either group has yet been found in the 
fied carboniferous material, crowded as it is with all Kinde ef 
vegetative remains in which the most delicate tissues are often 
preserved. In fact the fossil records, as a whole, lend no sup- 
rt to the view, so often ma aintained on purely “arte 
grounds, that the anes plants owed their origin to ryo- 
phytic ancestry.” (Progressus Rei Botanicae, 1907). He then 
that in the tertiary and later formations ties rworts are occa- 
sionally met with, but all the forms discovered are closely 
allied to existing species and throw no light on the origin o 
the Hepaticae. This disposes of the palaeontological evidence. 
Evidence from development within certain limits is some- 
times useful but great caution mets be used in drawing con- 
alone. Like mature structures 
developmental stages are also aes to variation especially 
when such stages are not concealed within elaborate protect- 
ing structures as is the case in Liverworts. Some examples of 
ares from this source roe occur in the course of this 
addres 
Thus our main evidence is aia from the comparative 
morphology of living plants. Here again it must be emphas- 
ised that generalisations from too small a number of forms are 
apt to be mistaken. This is one of the points which has been 
— —— home by the discovery of some Himalayan 
forms by the writer. 
In considering a number of forms belonging to any par- 
ticular group it is often possible to arrange them in a series 
