PLANT TAXONOMY IN AN AGE OF EXPERIMENT 585 



morphology have not proven to be the general panacea that some of their 

 early sponsors predicted, they have provided exceedingly useful classificatory 

 data, and the inclusion of information on karyotype has become a common- 

 place in taxonomic papers. Chromosome number has been particularly help- 

 ful in flagging anomalous situations and pointing up problems of polyploidy, 

 supernumerary chromosomes, and the like. Intensive investigation of such 

 cases by experimental means has not infrequently revealed a good deal about 

 the nature of natural populations and the origin and establishment of new 

 taxa. As the body of cytological information grows — witness the compendia of 

 Tischler (1950), Delay (1951), and Darlington (1945, 1955)— the more 

 readily can it be applied to taxonomic ends. The taxonomist should always 

 be aware, however, that such cytological information may be worthless or even 

 misleading when it is not properly documented by voucher specimens. The 

 comparative study of such cell types as trichomes, stomatal members, and 

 sclereids also holds considerable promise. 



It has always been assumed that if we had before us the whole fossil record 

 of vascular plants, we should be able to reconstruct a complete phylogeny of 

 their living descendants. Lam, for instance, says dogmatically that phylogeny 

 is paleobotany and all else is at best pseudo-phylogeny. Almost from the time 

 it was decided that fossil impressions were not works of the Devil to delude 

 True Believers, but had some natural reference to previous life on the Earth, 

 paleobotany has been coloring our ideas about relationships of organisms and 

 contributing to our essays at phylogenetic reconstruction. The main difficulty 

 is always that the material preserved is so sparse, so fragmentary, and so lack- 

 ing in critically diagnostic characters that much of it is subject to radically 

 divergent interpretations. Fossils often seem to be lacking just where we 

 could use them most profitably to show the branching of phyletic lines and 

 to link together now discrete and anomalous groups. It is also possible, of 

 course, that we are frequently searching for certain kinds of things that never 

 existed either on land or sea! The application of an ecological approach to 

 paleobotany, despite its dangerous assumption of long-term genetical and 

 physiological stability, has served as a wholesome corrective to a purely gross 

 morphological approach to fossil identification. Recent advances in the study 

 of fossil microspores, epidermis, and wood suggest that it is far too early to 

 conclude that all the evidence is now in and that the past is a permanently 

 closed book. 



If there is a measure of justification in the complaint of some workers that 

 it is basically unsound to interpret the structures of living and extinct lower 

 vascular plants in terms of those of living angiosperms, it would seem equally 

 tenuous to try to derive angiosperm features solely from those of Devonian 

 cryptogams — the origin of the magical "telome." A recent article in the 

 journal Evolution (LeClercq, 1956) points to the existence of a body of 

 Silurian and Cambrian vascular plants that were by no means psilophytalean, 



