September 28, 1906.] 



SCIENCE. 



399 



Professor Smith's work is certainly a good 

 book for good students, and as such is to be 

 heartily welcomed. H. L. Wells. 



SCIENTIFIC JOURNALS AND ARTICLES. 



The Botanical Gazette for August contains 

 the following papers : ' The Nascent Forest of 

 the Miscou Beach Plain,' by W. F. Ganong, 

 being the fourth contribution to the ecolog- 

 ical plant geography of the province of New 

 Brunswick ; ' The Development and Anatomy 

 of Sarracenia/ by Forrest Shreve ; ' Physio- 

 logically Balanced Solutions for Plants/ by 

 W. J. V. Osterhout ; ' The Appressoria of 

 the Anthracnoses,' by Heinrich Hasselbring; 

 ^ Nereocystis Lueikeana/ by Theodore C. 

 Frye, being a biological study of this giant 

 kelp; 'New Species of Castilleja and Senecio,' 

 by J. M. Greenman. The September number 

 contains the following papers : ' Differentia- 

 tion of Sex in Thallus Gametophytes and 

 Sporophytes,' by A. F. Blakeslee, being a gen- 

 eral discussion of sexuality in all the plant 

 groups ; ' The Development of the Bouteloua 

 Formation,' by H. L. Shantz, being the second 

 contribution from his study of the mesa region 

 east of Pike's Peak ; ' Cortinarius a Mycor- 

 hiza-producing Fungus,' by C. H. Kaufmann, 

 in which a new species of the genus is de- 

 scribed that is connected with three forest 

 symbionts belonging to different families ; * A 

 New Fungus of Economic Importance,' by R. 

 E. Smith and Elizabeth H. Smith, being a 

 new genus (Pythiacystis) parasitic on lemons 

 and causing a decay of green fruit trees and 

 in the storehouse. 



DISCUSSION AND CORRESPONDENCE. 



DISCONTINUOUS VARIATION AND PEDIGREE 

 CULTURE. 



Referring to the recent address of Dr. D. 

 T. MacDougal, on 'Discontinuous Variation 

 and Pedigree Culture' (published in The 

 Popular Science Monthly for September), the 

 following points may be worth considering: 



The species is the unit of the taxonomist, 

 and the study of species and their relations 

 to environment form the basis of the science 

 of distribution. 



The species, as thus considered, is a kind 

 of animal or plant as it has developed and 

 as it appears in a state of nature. To know 

 a species as it appears is not to know it com- 

 pletely, as all species develop differently un- 

 der changed conditions or freed from the stress 

 of competition. Under domestication, -or un- 

 der new chemical or physical conditions, all 

 species are plastic, and all may assume forms 

 the same species can never assume in its 

 original habitat. 



The field naturalist can not therefore know 

 everything about any species, no matter how 

 many individuals he may examine. Neither 

 can a garden naturalist, for the forms he deals, 

 with must be ' reduced to the ranks ' before 

 they are comparable to the species occurring 

 in the wild. 



It is presumable that those naturalists know 

 most about species as they are, who have given 

 most time and thought to their study. They 

 may not, however, know better than any others 

 how species originate, nor possess the clue to 

 the main causes or significance of their vary- 

 ing forms. 



Yet it is fair to say that as the taxonomist 

 of species finds in practically every case a geo- 

 graphical element in the development; as he 

 finds that segregation and selection have ap- 

 parently been accompaniments of nearly all 

 changes in species, and as by these same 

 agencies all species can be appreciably 

 changed by the will of man, he may not un- 

 reasonably suppose that segregation and selec- 

 tion have each taken some part in that life- 

 adaptation which we call organic evolution. 



As a zoologist personally acquainted with 

 Dr. de Vries the writer has great reverence 

 for the noble modesty, the patient, intelligent 

 and epoch-making perseverance which have 

 characterized his work. On the other hand, 

 he is obliged to hesitate at the acceptance of 

 the more sweeping parts of his theory, and to 

 question the assumption that the discoveries 

 of de Vries in plant mutation disclose the ac- 

 tual method of species-forming, general or 

 universal, in all branches of life. 



As matters are the species that exist in na- 

 ture must furnish us our conception of species. 

 The species actually covering the earth are 



