586 CONSTANCE 



and yet greatly antedate Rhynia and Hornea and Asteroxylon, which thereby 

 forfeit their unique basal position. Systematic paleobotany would appear to 

 set some limits to our phylogenetic thinking, but we should be wary in over- 

 rating what has been found as well as in overanticipating what may ultimately 

 be discovered. Meanwhile, I see no reason why we should not go as far as pos- 

 sible with other kinds of information. The true essence of Science is the con- 

 tinuous re-examination and testing of tentative conclusions. Paleobotanical 

 investigation should continue to provide us with important data for such re- 

 evaluation. 



No phase of biological advance has so drastically affected taxonomy in the 

 past half century as genetics and those cytological matters associated with 

 inheritance. I approach this portion of my resume with considerable trepida- 

 tion. The body of available information is tremendous, its applications to 

 systematics are currently filling and overflowing books and journals, and 

 there has grown up a mass of neo-orthodox doctrine which one dares to ques- 

 tion at his peril. Moreover, I cannot claim any mastery of the subject — yet 

 I wish to demonstrate that no taxonomist can afford to ignore it. 



The application of genetical information to taxonomy is sometimes based 

 upon the assumption that breeding behavior can establish the Truth about 

 relationships of organisms and that evidence gained in this way is entitled to 

 supersede all other indications of affinity. In the view of many, existence of 

 genetical compatibility establishes close phylogenetical relationship; incom- 

 patibility precludes it. Species and subordinate taxa can be defined on the 

 basis of fertility, sterility, and associated cytological behavior. Morphological- 

 anatomical criteria, not being "experimental," are of lesser moment and can- 

 not be allowed to gainsay genetical truth. A genetical system of classification 

 for at least the smaller taxonomic units can eventually be developed, with a 

 fine disregard of all other considerations, that will be "true." Evidence from 

 experimental crossing can at once tell us what has happened and what is 

 going to happen, and all else is irrelevant or permitted only probationary 

 status until it can be tested cytogenetically. Moreover, genetical evidence can 

 explain origins, migrations, and distributions and has already demonstrated 

 the essential correctness of the Wegnerian Hypothesis of wandering continents. 

 In view of these impressive attainments of our experimental colleagues, it is 

 small wonder that practitioners of descriptive botany are sometimes regarded 

 as hopelessly antiquated. 



Probably very few individuals would support all the propositions I have just 

 mentioned, but all have been advanced in one form or another in recent 

 decades. One will recognize in them, I think, the aura of enthusiasm and 

 missionary zeal which often accompanies new advances in any line of thought 

 or endeavor. We should not allow irritation at overstatement and intolerance 

 to blind us to the very real contributions that genetics and cytogenetics have 

 made to taxonomy. We have gained some knowledge of the methods by which 



