244 SECTIONAL ADDRESSES. 
angiospermous seed-plants, two wholly and others largely fossil.? In 
addition there are still a multitude of fossil forms, largely detached frag- 
ments such as sori, seeds, leaves, or wood, which are not sufficiently 
known or correlated to permit of their definite assignment to one or 
other of these classes. From these and for other discoveries it may 
well turn out to be necessary in the future to construct one or more 
new classes. 
Leaving these great series of vascular forms which played so 
dominant a part in the history of vegetation during the Primary and 
Secondary geological epochs, we may note that the gulf which has 
always existed for the phylogenist between Pteridophyta and Bryophyta 
is as wide and deep as ever, and that the same may be said of the gulf 
between the Bryophyta and the Alge. The attempts which have been 
made from time to time to derive various groups of Fungi from various 
groups of Algw seem to me quite unconvincing. The phylogeny of the 
Fungi themselves remains obscure, though certain lines of advance 
among them and among the Algz are fairly probable. On the whole 
the most successful phylogenetic speculations seem to me to be those 
that trace some at least of the classes of Algee back to a common origin 
in the great plexus of the Flagellata, which may also, perhaps, be 
regarded as the likeliest recognisable starting-point of the main lines 
of invertebrate evolution. Turning to the other extremity of the Plant 
Kingdom, to the characteristically modern dominant vegetation of the 
earth, we are scarcely able to form a trustworthy opinion as to the 
nature of the plants from which the two great modern groups of Angio- 
sperms sprang, though the speculations of one of my predecessors in 
this chair, the late Miss Sargant, founded on wide researches and elabo- 
rated with masterly ability, are certainly of great interest, and full of 
suggestion as to what may have occurred. The evidence from fossil 
Angiosperms is still unsatisfactory, and Mr. Hamshaw Thomas’s inter- 
esting discoveries of Jurassic Angiosperms scarcely throw light on the 
problem of the descent of the group. It has been the invariable history 
of such researches, pursued with a view to tracing phylogeny, that the 
better a newly discovered group has become known the less probably 
it appears to represent the common ancestors of other existing or fossil 
groups. The points of origin, the roots, so to speak, of each group 
have been constantly lengthened and shifted further back in geological 
time so that they become more definitely independent from one another 
and appear to issue separately from a past which remains obstinately 
obscure. ‘ It may be,’ said Professor Seward recently,° speaking from the 
fullness of a very wide knowledge of the floras of the past, ‘ that we shall 
never piece together the links in the chain of life, not because the missing 
parts elude our search, but because the unfolding of terrestrial life in 
all its phases cannot be compared to a single chain. Continuity in some 
degree there must have been, but it is conceivable that plant life viewed 
5 Pteridospermee, Cordaitales, Cycadophyta, Coniferales, Ginkgoales, and 
Gnetales : see Seward, Fossil Plants, vols. IIT. and IV. 
6 A. C. Seward, ‘A Study in Contrasts,’ (Hooker Lecture), Journ. Linn. Soc. 
Bot., October 1922, p. 238. 
