■May 6, 1921] 



SCIENCE 



439 



Primarily the Cretaceous floras looked 

 tropical, and it has been difficult to read any- 

 thing else into them. If it can be done it 

 will require long and elaborate quantitative 

 study of the phytologic factors. It would 

 however be early to say there are no cold 

 scrub forests in the lower Cretaceous, and I 

 give some attention to this subject in the 

 current April number of the American Jour- 

 nal of Botany. Then at tlie other end of a 

 long record stood juxtaposed the dank coastal 

 fringes of coal plants; whence the long series 

 of the Permian, Triassic and Jurassic, found 

 their more obvious antecedents in warm 

 climates and seemed to terminate in such. 

 The ginkgos were long almost the only ele- 

 ment suggesting interruption to the all-tropic 

 landscape, with the fact that they must be a 

 very great phylum, hidden. But with the 

 cycads dominant and certainly tropical, there 

 was no open sesame to a broader vista for the 

 paleobotan'ist. 



Now it was at this point that Nathorst and 

 Wieland, using the words of the excellent 

 University of Glasgow historian of botany, 

 " began to learn something about the cycads." 

 It was found that these had flowers with the 

 possibility of all the sex variation seen in 

 dicotyls, and stems with generalized structure. 

 A great Cycadophyte leaf series was discerned 

 resting under more than a suspicion of affinity 

 to the forerunners of the angiosperms. And 

 presently it was found that the cycadeoid 

 types were in great numbers microphyllous, 

 and that they crossed over into small fern- 

 like leaves called Tceniopteris, etc. Next the 

 paleobotanists seemed as if by common con- 

 sent to see side by side with the ever length- 

 ening cycadeoid record a great ginkgoid 

 phylum. Within but a few fortunate years 

 of investigation types of scrub, for such many 

 of the cycadeoids surely are, and forest ele- 

 ments with the capacity to live in varied 

 climates, could be jwinted out with some 

 d^ree of safety. 



But as a bare half dozen invertebrates can 

 not firmly set the age of the " Cannonbail 

 shales," limited series of animals and of 

 plants of unfixed affinity, can make neither a 



summer nor a winter. And so the difficulties 

 which beset the work on fossil plants must be 

 met serially. 



Meanwhile as paleobotanists we are pecu- 

 liarly indebted to Dr. Knowlton for his 

 splendid Philippic on tropic climates. It was 

 well that it should appear in this time of 

 rapid accumulation of new facts, at least as 

 a warning against the grave danger of an 

 overburden of inference in the guise of proven 

 fact. Even that big and valuable word 

 diastrophism might suffer. And the aggrad- 

 ing of the continents, with their reappearance, 

 mountain bulwarked as regularly as Chladni 

 figures, might fail of demonstration. The 

 Knowlton defense has already functioned in 

 bringing out the two accentuations of the 

 value of the physical and paleozoologic factors 

 herein noted. Tet, the lower-most Cretaceous 

 floras of the mid-west are not truly tropic. 

 "We may doubt if there is a single North 

 American dicotyledonous flora, unless it be 

 that associated with the Vicksburg Oligocene, 

 that by any possibility merits the term trop- 

 ical in a strict sense. " Many of the floras 

 indicate warmer or wetter conditions than 

 now prevail in correspondent latitudes; but 

 most are far from tropical." 



All evidence must eventually be coordinated, 

 and the paleobotanists will lay ears to the 

 rocks. To use exactly the witticism of Vol- 

 taire, let our conchiferous brethren be re- 

 assured. 



G. R. Wieland 



HAVE BIRDS AN ACUTE SENSE OF SOUND 

 LOCATION? 



There can be little doubt that the drum 

 membrane picks up very minute energies in 

 the form of sound vibrations. There can be 

 no question that a certain amount of the 

 energy impinging on the outer surface of the 

 drum membrane passes through it into the 

 air of a cavum tympani. It may also be con- 

 ceded that energies entering the middle ear 

 area are fairly well dampened out in so far as 

 a reflection back toward the drum membrane 

 is concerned. This is true for the mammals. 

 The bird, however, has but a single middle ear 



