May 10, 1895.] 



SCIENCE. 



525 



tious. The admissibility of the expansion 

 theorj' is based on the assumption that the 

 earth magma may expand on solidifying as 

 water does. The recent work of Barnes, 

 however, with which our author was proba- 

 bly not famiUar at the time he wrote, so in- 

 validates this assumption that it is no 

 longer worthy of serious consideration. 



A. C. Lawsox. 



UXIVEBSITY OF CALIFORNIA. 



Mesozoic Plants From Kosuke, Kit, Awa and 

 Tosa. By META.JIRO Yokoyoma, Professor 

 in the Imperial University of Japan. 

 In tliis paper, illustrated by nine plates of 

 good figures, and published as part III., 

 Vol. VII., of the Journal of the College of 

 Science, Imperial Uuiversitj' of Japan, Pro- 

 fessor Yokoj'oma has given us a valuable 

 addition to our knowledge of the lower Cre- 

 taceous flora. The plants of this age, 

 known for a long time mostly in their 

 Wealden types, and from a few localities in 

 England and on the continent of Europe, 

 have, by recent discoveries, been greatly in- 

 creased in number and variety. The extent 

 of the territory kno^\Ti to have been occu- 

 pied by them has of late been still more 

 notably enlarged. We now know lower 

 Cretaceous plants from such widely sepa- 

 rated series of strata as the Potomac of the 

 Atlantic States : the Comanche series of 

 Texas, the coal group of Great Falls, Mon- 

 tana ; the Kootanie series of British Co- 

 lumbia ; the Shasta group of California ; the 

 lower strata of Newton's Dakota gi-oup in 

 Dakota and Wyoming. Professor Yoko- 

 yoma's investigations add still another 

 region on the Asiatic side of the Pacific, and 

 make it probable that the lower Cretaceous 

 flora was in Asia no less important than it 

 was in Xorth America. These additions 

 are especially gi~atifying, as the flora of this 

 time was the last one in which angiosperms 

 did not predominate. It is the flora of an 

 era when predominating Mesozoic elements 



were about to dis;\ppear forever. If we are 

 ever to learn what changes caused a flora 

 consisting only of Equiseta, Cycads, Ferns 

 and Conifers to give way to one in which 

 angiosperms overwhelmingly predominate, 

 and in which all these groups, except the 

 conifers, play an insignificant part, we shall 

 most probably find the solution of this as 

 yet unsolved problem from the examination 

 of lower Cretaceous plants. 



In 1890 Prof. Nathorst, of Stockholm, ex- 

 amined a number of fossil plants from Shi- 

 koku, Japan, and determined their age to 

 be either upper Jurassic or Wealden. Pro- 

 fessor Yokoyoma states that he was induced 

 to carry the investigation of this flora far- 

 ther than the Swedish paleontologist had 

 done, with the hope of fixing more definitely 

 its age. In consequence of tliis he col- 

 lected not only from the localities of Nath- 

 orst, but fi'om several others showing a 

 similar flora. He succeeded in adding a 

 number of species not seen by Nathorst, 

 and in procuring, in some cases, better 

 specimens of those previously obtained. 

 In this way the total number of species was 

 brought up to 26, with 2 varieties. It is 

 noteworthy that, while the flora is without 

 doubt lower Cretaceous in age, as Professor 

 Yokoyoma determines it to be, it contains 

 no angiosperms. He identifies several of 

 the species with certain ones found in the 

 lower Potomac strata of the eastern United 

 States. He states his conclusion as to the 

 age of the plants in the following words : 

 " I go a step farther than Professor Nath- 

 orst and saj' that the plant-bearing beds of 

 Kozuki, Kii and Shikoku represent the 

 whole Neocomian series, corresponding to 

 the Potomac of Americji. ' ' This statement, 

 so far as the Potomac is concerned, would 

 be more correct if it made the Japanese 

 beds correspond to the loiver Potomac. Amer- 

 ican geologists now mclude in the Potomac 

 the Tuscaloosa group and the South Amboy 

 series of beds, both of which contain few, if 



