V^OL. 43 T O R R E Y A July 1943 



Modern Taxonomy and Its Relation to Geography* 



Henry K. Svenson 



Taxonomy in the last sevent\'-five years has had increasingly close connec- 

 tions with geography, but the subject is so vast that only a small portion of the 

 field can be covered at this time. The most that can be done is to review some 

 of the geographical theories that have been in the light for two decades or more, 

 and with which we all are more or less familiar. These subjects are so inter- 

 twined that separate discussion of any of them is difficult and all of them are 

 but loose ends of the tangled thread that represents our fund of knowledge of 

 plant geography. 



As to geographical location, we are practically astride the terminal glacial 

 moraine which runs the length of Long Island, and which was a collecting 

 ground for Asa Gray when he was associated with Torrey in Xew York. !Much 

 ink has flowed on the subject of glaciation and its effect on plants since Gray 

 published his remarkable report on the similarities of the flora of eastern Asia 

 and eastern North America, in 1859. This date, which coincides with that of 

 the "Origin of Species," was only eight years before the founding of the Torrey 

 Club, which can therefore be said to have occupied practically the whole 

 period of modern biology. Gray's remarks were based on a collection by Charles 

 Wright, who is also well-known for his collections in Cuba and for those in his 

 own part of the Torrey Club Range, in Hartford, Connecticut. 



As every taxonomist knows, the genera and even many species which we 

 find in our southern Appalachians are the same as those of the mountains of 

 western China and of Japan. The following quotations are from Gray's paper, 

 Amer. Acad. xA.rts and Sci. Mem. 6: 1859: "The fundamental and most diffi- 

 cult question remaining in natural history is here presented ; the question 

 whether this actual geographic association of congeneric or other nearly rela- 

 ted species is primordial and therefore beyond all scientific explanation, or 

 whether even this may be to a certain extent a natural result. The only note- 

 worthy attempt at a scientific solution of the problem is that of Mr. Darwin and 

 Mr. Wallace,^ partially sketched in their short papers, 'On the Tendency of 

 Species to Form Varieties ; and on the Perpetuation of Varieties and Species 

 by Natural Means of Selection' " (p. 443). 



"At length, as the post-tertiary opened, the glacier epoch came slowly on — 

 an extraordinary refrigeration of the northern hemisphere, in the course of ages 

 carrving glacial ice and arctic climate down nearly to the latitude gf the Ohio. 

 The change was evidently so gradual that it did not destroy the temperate flora, 



* Read at the 75th Anniversary Celebration of the Torrey Botanical Oub at The Xew 

 York Botanical Garden, Tuesday, June 23, 1942. 

 • ^ Journ. Linn. Soc. (Zoology). 3: 45. 1858. 



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