188 BROOKLYN BOTANIC GARDEN MEMOIRS 
Brongniart and his contemporaries and successors erected the super- 
structure which gradually developed into the science of paleobotany 
as we now recognize it. 
The first great basic fact, therefore, that paleobotany proclaimed 
was that our living flora had an ancestry whose elements were different 
from those now in existence. As facts accumulated, and the floras of 
the successive periods in the earth’s history became better and better 
known, the phylogenetic development from low and simple types of 
vegetation to successively higher and more complex ones was demon- 
strated, and a rational, philosophical basis for systematic botany was 
established. Before that time any system of taxonomic arrangement 
of the vegetable kingdom was purely theoretical. Relationships 
were recognized, but they were often lacking in explanation; and it 
is significant that every real advance which has been made in tax- 
onomy has been in accord with our constantly increasing knowledge 
of phylogeny. Paleobotany is thus constantly helping to solve the 
broad problem of the why and wherefore of our modern systematic 
arrangement of the vegetable kingdom and rendering it more and more 
truly scientific. 
If certain of the apparent anomalies in modern taxonomy are 
critically examined in the light of paleobotanical knowledge they 
become anomalies no longer. As an example we may consider the 
case of a monotypic genus such as Ginkgo. It is represented by a 
single living species, G. biloba L., and its nearest affinities among living 
coniferae are apparently with the Taxaceae. What is the meaning of 
its isolation in our scheme of classification? Does it represent a recent 
development of a new generic type in connection with which new 
species are destined to be evolved in the future, or does it represent 
an ancient type of vegetation of which it is now the sole survivor? 
Paleobotany has supplied the answer to these questions by demon- 
strating that the genus was formerly represented by many species and 
that it was merely one of a number of allied genera all of which are 
now extinct. 
The genus Sequoia, with its two living species, is a similar, although 
not quite so striking an example of generic isolation; and in the same 
category may be mentioned Nelumbo, Liriodendron, Sassafras—each 
represented by but two species—and Liquidambar by three. All of 
these represent vanishing generic types as evidenced by the many 
known fossil species in each, now entirely extinct. It was, of course, 
reasonable to infer that such was the case in these and other similar 
instances; but paleobotanical discoveries alone furnished the definite 
proof. 
It is, however, within the domain of what we broadly designate as 
