438 



SCIENCE 



[N. S. Vol. LIII. No. 1375 



frigid climates now reign. Aimual rings are 

 rarely found in the trees, and only once before the 

 Pleistocene is a period of severe cold admitted in 

 the early Permian time of glaoiation ; and then 

 the cold period was "probably of short duration," 

 and did not affect North America, Europe or 

 northem Asia. 



It is further observed that while few 

 references to periods of cold or drought in the 

 world's history are found in paleobotany, 

 " mild and moist periods are tremendously 

 emphasized," and intervening periods of 

 drought and cold " slurred over, or entirely 

 unrecorded." 



It is not surprising, then, that the evidence 

 for aridity and cold during several periods 

 of the earth's history should make little im- 

 pression on a paleobotanist ! 



In somewhat similar inference or vein. Pro- 

 fessor Charles Schuchert follows with several 

 pages on climatic evolution. To Coleman's 

 brief consideration of the more readable 

 phases in the evidence for desert conditions 

 seasonal variations, and ice ages in the past, 

 Schuchert adds the Blackwelder view that a 

 study of the color phases and stratification of 

 the Alaskan sedimentary series indicates a 

 more or less persistently cool moist climate 

 throughout the known geologic history of 

 Alaska. And the more or less provable fact 

 is emphasized that there is usually " a dearth 

 of plant evidence for the climatic conditions 

 during the early and late parts of the many 

 periods when the continents were largest, 

 highest and most arid." 



For several years I have called attention to 

 the remarkable series of Rhatic plant localities 

 in Argentina which strongly suggest a climate 

 like that of to-day. And too, the shales in 

 which these plants occur are highly laminated 

 [seasonally so]. But in such instances, which 

 may be depended upon to multiply, the paleo- 

 botanist must yet find the fuller means of 

 proving the presumption of cold and aridity 

 from plant types, however insistently others 

 may ask immediately coordinated proof. 

 Similarly it was stated in Science several 

 years ago that: 



Thea-e is a very small record of the upland vege- 

 tation of past times; although the enormous ex- 

 tent of the unknown ^upland record could not be 

 surmised so long as the alternate emergence and 

 suibsideuce of the continental areas remained 

 wholly unmapped. Yet it appeairs that the high 

 upland and polar, and not the trotp-ic or coastal 

 fringe plants have long included the great major- 

 ity of plastic forms; and it is certain that upland 

 and polar ftorms moved forward during the pe<riods 

 of continental emergence closing the geologic 

 epochs, and weTe least liable to extinction during 

 medial subsddeaice. That ds to say we know best 

 the aplastic coastal fringe forms with a broken 

 record. 



Again it was stated (Vol. II., p. 238, Amer- 

 ican Fossil Cycads) : 



Almost invajiaJbly from the Devonian on, it has 

 been mainly xerophyllous lacustrine or swamp 

 types which form the great bulk of fossil plants. 

 Even the 3,000 species of Carboniferous time af- 

 ford only a one-sided picture of the specialized 

 coal swamp floras ; no glimpse is had of contempo- 

 rary mountain or upland florulea. 



Furthermore the notion that the tepid 

 climates of the older botanists and zoologists 

 have no basis (Berry), and are not sustained 

 by the long studied invertebrate record, only 

 finds a more insistent expression in recent 

 text books. It goes back to Leopold von Buch, 

 and received elaboration by Neumayr. It 

 finds so far as elements go mention in Dana. 

 It was stated to me in pretty hard and fast 

 form in the field as a beginning student, by 

 an old teacher, A. von Konen, twenty-eight 

 years ago. And any one who takes the trouble 

 to read a contribution I brought out in 1903, 

 on the role of polar climates in evolution, 

 then a sort of philosophic study, can well 

 understand that the ideas of the real char- 

 acter of sediments and the indicators of sea- 

 sonal change which are quite in entirely of 

 more recent date, would have been " old grist " 

 for the polar mill. 



As a main objective, let me try to explain 

 in a few brief paragraphs for the sake of both 

 botanists and geologists the nature of the 

 paleobotanic crux. 



