294 MORPHOLOGY OP ANGIOSPERMS 



bered that the whole theory is based upon the present concep- 

 tion of species, a conception so variable that it can not be 

 defined. Furthermore, although there may be a fixed limit 

 to ordinary variation, there must also be a fixed limit to the 

 extraordinarv variation called mutation, and this remains to be 

 defined. In fact, there is evidence that extreme mutation re- 

 sults in functional derangement of organs, and the result is a 

 monstrosity, which may be regarded as an impossible new spe- 

 cies. Finally, even if mutation be found to explain the origin 

 of many new species, it does not follow that other processes 

 also may not be working to the same result. 



In a recent paper, Strasburger 19 takes occasion to discuss 

 the origin of species, taking the view that the results of natural 

 selection have been overestimated, and that new species have 

 arisen through mutation, due to internal causes alone, and 

 through " use and disuse," by means of which a certain amount 

 of adaptation to environment is secured. To him the only func- 

 tion of natural selection appears to be to remove the less valu- 

 able forms produced through mutation and " use and disuse." 

 It follows that the ordinary physiological operations do not 

 result in species, but affect them after they have appeared, and 

 that the origin of species is a morphological rather than a phys- 

 iological problem. 



LITERATURE CITED 



1. Bower, F. O. A Theory of the Strobilus in Archegoniate Plants. 



Annals of Botany 8 : 343-365. 1894. 



2. Delpixo, P. Applicazione de nuovi criterii per la elassificasione 



delle piante. Mem. Real. Accad. Sci. Bologna V. 6: 83-116, 

 1896 ; see review Bot. Central bl. 67 : 370. 1896. 



3. Bessey, C. E. Phylogeny and Taxonomy of the Angiosperms. 



Bot. Gazette 24: 145-178. 1897. 



4. Klebs, G. Alternation of Generations in the Thallophytes. An- 



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5. Lang, W. H. Alternation of Generations in the Archegoniates. 



Annals of Botany 12: 583-592. 1898. 



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7. Holm, Theo. Podophyllum peltatum; a Morphological Study. 



Bot. Gazette 27 : 419-433. figs. 10. 1898. 



8. Coulter, J. M. The Origin of the Leafy Sporophyte. Bot. 



Gazette 28: 46-59. 1899. 



