172 



field of research Dr. Hilgard modestly credits Owen and Peter 

 with being the pioneers in this country, but his own splendid 

 " Report on the Geology and Agriculture of Mississippi" (printed 

 in i860, but unfortunately not generally distributed until several 

 years later *) is far ahead of anything previously published in that 

 line. It is undoubtedly the first work in which the floristic dif- 

 ferences between the several longitudinal subdivisions of the 

 coastal plain t are clearly pointed out, and it remains to the present 

 day the most complete description of the vegetation (as well as of 

 the geology) of Mississippi ever published. | 



In the new book, as in some of his previous publications, the 

 author lays stress upon the principle that in regions of ample rain- 

 fall, like the Eastern United States, variation in the amount of 

 lime in the soil is one of the chief causes of local diversity of vege- 

 tation ; while in arid regions, where nearly all soils are calca- 

 reous, the effect of moisture is more conspicuous. This perhaps 

 explains why most of the studies of the relations between geology 

 and vegetation hitherto made in this country have been in the 

 East, while ecologists living on the Plains are inclined to regard 

 water-content of the soil as all-important. 



The first chapter of part 4 is practically a condensation and 

 revision of the author's observations in Mississippi previously 

 published in the i860 report just mentioned and in the fifth vol- 

 ume of the Tenth Census twenty-four years later. ' Regarding 

 vegetation as essentially stationary, he points out the striking 

 differences between the natural growths on calcareous and non- 



*See Am. Jour. Sci. II. 32: 303. 1861 ; Tenth Census U. S. 5: 67, 201. 

 1884; Am. Geol. 27 : 284-31 1. 1901 ; Bull. U. S. Geol. Sun^ 283 : 5, 6. 1906. 



t In this connection it is noteworthy that the term " coastal plain " did not appear 

 in strictly botanical literature until ten or twelve years ago, and even yet many 

 American botanists do not realize its significance, and still more probably regard that 

 province as essentially a homogeneous one. 



:|: It was under his leadership that the two splendid volumes on cotton production 

 of the southern states and California were prepared for the Tenth Census. On ac- 

 count of their too modest title these volumes have never received the recognition from 

 scientists (except perhaps from geologists) that they deserve ; but they are remarkable 

 for their accuracy and completeness, and show in a most convincing manner how the 

 local distribution of forests, crops, and population in the Southeast depends mainly on 

 soil, rather than on temperature, latitute, altitude, or drainage basins, as some writers 

 in the North have assumed. 



