130 



SCIENCE 



[N. S. Vol. XXXTIII. No. 969 



occur in the southern and western parts of 

 North America," and for the genus, as a whole, 

 it is said that there are in the world " about 50 

 species, natives of the north temperate zone, 

 Mexico and the Andes of New Granada." In 

 the second edition 73 species are figured and 

 described from the same range, while the fol- 

 lowing statement is made for the genus as a 

 whole. " About 300 species, natives of the 

 north temperate zone, the tablelands of Mex- 

 ico and the Andes; the center of distribution 

 is the eastern United States." The genus has 

 been of great taxonomic interest for ten years, 

 about 1,000 species having been described from 

 the United States during that period. Data 

 are fast accumulating tending to show that 

 many of these newly described species are 

 hybrids. 



In the Introduction (pp. ix, x) one finds the 

 following condensed version of the " American 

 Code," which takes the place of the longer 

 statement in the first edition: 



1. The nomenclatorial type of a species or sub- 



species is the specimen to which the describer 

 originally applied the name in publication. 



(a) When more than one specimen was origi- 

 nally cited, the type or group of speci- 

 mens in which the type is included may be 

 indicated by the derivation of the name 

 from that of the collector, locality or host. 



(6) Among specimens equally eligible, the type 

 is that first figured with the original de- 

 scription, or in default of a figure the 

 first mentioned. 



(c) In default of an original specimen, that 

 represented by the identifiable figure or 

 (in default of a figure) description first 

 cited or subsequently published, serves as 

 the type. 



2. The nomenclatorial type of a genus or sub- 



genus is the species originally named or 

 designated by the author of the same. If 

 no species was designated, the type is the 

 first binomial species in order eligible under 

 the following provisions: 

 (g) The tjrpe is to be selected from a subgenus, 

 section or other list of species originally 

 designated as typical. The publication of 

 a new generic name as an avowed substi- 

 tute for an earlier invalid one does not 

 change the type of a genus. 



(6) A figured species is to be selected rather 

 than an unfigured species in the same 

 work. In the absence of a figure, prefer- 

 ence is to be given to the first species 

 accompanied by the citation of a speci- 

 men in a regularly published series of 

 exsiccatae. In the case of genera adopted 

 from prebinomial authors (with or with- 

 out change of name), a species figured 

 by the author from whom the genus is 

 adopted should be selected. 



(c) The application to a genus of a former 



specific name of one of the included spe- 

 cies, designates the type. 



(d) Where economic or indigenous species are 



included in the same genus with foreign 

 species, the type is to be selected from 

 (1) the economic species or (2) those 

 indigenous from the standpoint of the 

 original author of the genus. 



(e) The types of genera adopted through cita- 



tions of nonbinomial literature (with or 

 without change of name), are to be se- 

 lected from those of the original species 

 which receive names in the first binomial 

 publication. The genera of Linnsus's 

 "Species Plantarum" (1753) are to be 

 typified through the citations given in his 

 "Genera Plantarum" (1754). 



Enough has been said to show that the new 

 edition differs so much from the earlier one 

 that it must find a place upon the shelves of 

 every botanical library. 



It only remains to be said that while the new 

 edition was passing through the press Judge 

 Brown closed his labors, but not before he had 

 seen the pages of the new book. To the sur- 

 viving author we must offer our congratula- 

 tions upon the publication of the present edi- 

 tion. 



Charles E. Bessey 



The UNrvEESiTY of Nebraska 



The Mathematical Theory of Heat Conduc- 

 tion. By L. E. Ingersoll and O. J. Zobel. 

 Ginn & Co., Boston. 171 pages. 

 The accurate solution of problems in heat 

 transmission has been neglected in the past 

 by engineers. They have been content to ar- 

 rive at approximate results by empirical meth- 

 ods or by guessing. With the increased use 



