Mat 11, 1906.] 



SCIENCE. 



737 



SCIENTIFIC BOOKS. 

 Status of the Mesozoic Floras of the United 

 States. By Lester F. Ward. Second 

 Paper, witli the collaboration of William 

 Fontaine, Arthur. Bibbems and G. R. Wie- 

 LAND. U. S. Geological Survey, Monograph 

 XLVIII., 1905. Part I., text, pp. 616; 

 Part II., plates I.-CXIX. 4to. 

 This valuable contribution to the paleon- 

 tology of North America, and particularly of 

 the United States, appears as a sequel to an 

 earlier publication on the Older Mesozoic,' 

 and forms the second in a series of which the 

 third is yet to appear. Like the previous pub- 

 lication, the present one deals with the floras 

 of widely separated localities and with a some- 

 what similar range of horizons. It is divided 

 into three parts: Part I. deals with the Trias- 

 sic Flora as presented by the Older Mesozoic 

 of Arizona; Part II. discusses the Jurassic 

 Flora of Oregon, Wyoming and the Black 

 Hills, as well as the transition floras of 

 Alaska, California, Montana and Oregon; 

 Part III., which occupies the largest share of 

 the volume, is devoted to the Cretaceous Flora 

 as presented in the Queen Charlotte Islands, 

 the Kootanie of Montana and British Colum- 

 bia, the Lakota (Kootanie) of the Black HiUs, 

 the Trinity of Texas and the Older Potomac 

 of Maryland and Virginia. The flora of the 

 Black Hills having been dealt with somewhat 

 fully in a previous paper," the present account 

 is somewhat brief, discussing supplementary 

 data which are, nevertheless, of considerable 

 importance. If any estimate of comparative 

 value were to be made, it would be in favor 

 of Part III., because of the important results 

 reached with respect to evidence bearing upon 

 the correlation of the Potomac in various 

 localities and its precise relations to the 

 Jurasso-Cretaceous. 



The opening chapter deals somewhat briefly 



^ Ward, Lester F., ' Status of tlie Mesozoic 

 Floras of the United States.' First Paper: The 

 Older Mesozoic. U. S. Geol. Surv., XX., Part II., 

 1898-1899, pp. 215-430, pi. XXI.-CLXXII. 



^ Ward, Lester F., ' The Cretaceous Formation 

 of the Black Hills as Indicated by the Fossil 

 Plants.' U. S. Geol. Surv., XIX., 1897-1898, pp. 

 527-712, pi. LVII.-CLXXII. 



with the Triassic, or the Older Mesozoic flora 

 of Arizona, based upon data secured by an 

 expedition executed in May and June of 1901. 

 While the results obtained were especially rich 

 in vertebrate paleontology, some important 

 observations were made with respect to the 

 occurrence of plant remains which were, 

 nevertheless, found to be exceedingly scanty. 

 This appears to be accounted for by the great 

 abundance of gypsum that prevails through- 

 out all the beds of the region, a material which 

 is fatal to the preservation of more delicate 

 plant remains, and in consequence it is only 

 the silicified wood that seems to have escaped 

 its influence. Furthermore, such silicified 

 woods are mainly deposited in beds of sand, 

 coarse gravel or conglomerate, which in them- 

 selves are unfavorable to the preservation of 

 plant impressions. As the petrified forests 

 have been reported upon at length on a former 

 occasion," and as the structure of the woods 

 has been worked out by EJaowlton,' at least in 

 part, they do not claim special attention. 

 Nevertheless, there are frequent references to 

 the abundant occurrence of fossil woods which 

 would presumably afford an opportunity for 

 an important extension of our knowledge re- 

 specting extinct species; but the impression 

 conveyed to the reader is that the investigator 

 gave somewhat scant heed to this most im- 

 portant material, attaching far more value to 

 mere leaf impressions, fruit and other forms 

 of remains. The impression thus gained is 

 heightened by the want of any sort of refer- 

 ence to the working up of the wood, except 

 such as may be found in the statement that 

 ' The only species that has yet been described 

 from the silicified wood of Arizona is Arau- 

 carioxylon arizonicum of EJnowlton, based on 

 specimens from these two trunks.'" 



' Ward, Lester F., ' Status of the Mesozoic 

 Floras of the United States.' U. S. Geol. Surv., 

 XX., 1898-1899, pp. 316-332. 



* Knowlton, F. H., ' New Species of Fossil Wood 

 lArauearioxylon arizonicum) from Arizona and 

 New Mexico,' Proc. U. 8. Nat. Mus., XI., 1888, 

 pp. 1-4. 



^ This reference is to two great logs taken to 

 the National Museum in 1880 or 1881, from 

 Lithodendron Creek, by an expedition headed by 

 Lieut. J. T. 0. Hegewald in the spring of 1879. 



