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 Neliimho, 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 



