The Ancestry of the Cypress. 39 



physical condition upon the water and air of the soil will be dis- 

 cussed in a later paper. 

 Bureau of Soils, 

 U. S. Department of Agriculture, 

 Washington, D. C. 



NOTES ON THE ANCEvSTRY OF THE BALD CYPRESS. 



Edward W. Berry. 



It may be stated as an axiomatic fact that when we find a 

 monotypic genus in the existing flora, or one with but few species 

 widely separated geographically from their nearest kin, the genus 

 in question has a most interesting geological history which 

 reaches back into the past much farther than does the ancestry 

 of the horse or the camel, and that at some time the gaps in the 

 present geographical distribution were occupied by the species 

 in question or their immediate ancestors. 



Familiar instances of plant survivors of an ancient lineage — - 

 extending back sometimes to the remote Paleozoic, will readily 

 suggest themselves. Such a one is the well-known Ginkgo or 

 Maidenhair tree of our parks. Others, like the Sequoia or the 

 Sassafras or the Tulip-tree, are almost equally notable even if 

 they do not reach back quite so far into the past. Another prin- 

 ciple which we usually lose sight of when we speak of plant 

 migrations is the fact that present similarities between geogra])h- 

 ically remote areas do not represent a comparatively recent 

 interchange of species between those areas. What they really 

 show is that a former more or less cosmopolitan distribution has 

 become greatly restricted and the former connecting links in 

 the continuous series of forms have been exterminated in the 

 intervening areas. As a case in point we may take the well- 

 known and often remarked similarity between the floras of 

 eastern Asia and eastern North America. What this has been 

 supposed to represent by plant geographers was a progressive 

 latitudinal migration which might have occurred in an east or 

 west direction from either Europe, Asia, or America as the 

 original starting point. A study of prehistoric floras shows that 



