712 



SCIENCE. 



[N. S. Vol. XXII. No. 570. 



gathered by Mr. Stabler on Bowfell which 

 comprises five species of Marsupella inter- 

 mingled in the space of a square inch." Be 

 it remembered that Spruce was a most critical 

 student of these forms. 



x\nd, if these are proper examples, what of 

 the numerous species of oaks, willows, thorns, 

 asters, golden-rods and many others which 

 spring up in hosts to challenge our scrutiny? 

 Certainly we should think long before apply- 

 ing the principle advocated by President 

 Jordan to these. And what too, shall we say 

 of the many species of the Siphonese, the sea- 

 fans, shaving-brushes and their like which 

 grow in the warmer waters of the tropics, 

 many closely related kinds in restricted and 

 identical localities!, a condition quite anal- 

 ogous, I venture to say, to the distribiition of 

 the oaks, willows, et cetera. 



It therefore appears that the general law 

 as stated by President Jordan, ' Given any spe- 

 cies in any region, the nearest related species 

 is not likely to be found in the same region 

 nor in a remote region, but in a neighboring 

 district separated from the first by a barrier 

 of some sort,' would be more in harmony with 

 the facts in the case as understood by the 

 botanists if stated in the converse form. 



President Jordan further admits that, theo- 

 retically, mutations may arise which may hold 

 their own in competition with the parent form, 

 but states that stich a condition is virtually 

 unknown.* This, however, is far from being 

 the case among the plants. Aside from the 

 many properly designated species in cultiva- 

 tion, we have definite, well-authenticated cases 

 of uncultivated forms which give denial. 



In 1886, de Vries found in the fields of 

 Hilversum a plant, (Enothera irevistylis, 

 which turned out to be a mutant of 0. 

 LamarcTciana. Although 0. hrevistylis pro- 

 duces comparatively few seeds compared with 

 the parent form, and has not arisen anew as 

 a mutant since the time of its discovery, it 

 has, nevertheless, been able to maintain itself 

 alongside the parent species in the original 

 habitat up till the present time. 0. hrevistylis 



^ Rev. Bryologique, 8: 104. 

 ^L. c, p. 545. 



1881. 



may be artificially crossed with the parent 

 form and when this is done the progeny split 

 according to the Mendelian principle, so that, 

 even if this were the means of propagation 

 upon which 0. hrevistylis depends, the race 

 would be maintained. 



Without recounting the case of Capsella 

 Ileegeri, and other well-known instances which 

 are completely authenticated, we may see that 

 it is unwise for us to ignore the probability 

 that the same thing has occurred in nature 

 very many times. 



The examples which I have given above are 

 only a few of a thousand which might just as 

 easily be recited and have occurred out of hand 

 to me and to a few of my colleagues whom I 

 have questioned on the matter. 



Apropos of the proposition^ that all the 

 organisms in a region unbroken by barriers 

 will slowly change together in the process of 

 adaptation by nature, I may be permitted to 

 point out that it is again still an open ques- 

 tion whether this is the method by which a 

 peculiar flora has attained its apparent uni- 

 formity. Curiously enough we find markedly 

 desert types, e. g., Zyzyphus, a thorny shrub 

 of the desert, growing chiefly along water 

 courses, and opposite types, as Yerhena ciliata, 

 which can not be seen to differ from a so- 

 called ' mesophytic ' garden weed, ecologically 

 or physiologically, getting along quite well in 

 the habitat of Cereus giganteus, the ocotillo 

 (Fouquieria splendens) and a lot more special- 

 ized enough plants. • Similarly we find, for 

 examples, a species of Opuntia, 0. Opuntia, 

 growing in our eastern states associated to- 

 gether with mesophytes, just as we find many 

 mesophytes growing in arid deserts. Why? 

 The answer to this query involves some 

 answer to the problem of the origin of desert 

 floras, one, however, which has not yet been 

 solved. F. E. Lloyd. 



Teachees College, 

 Columbia Univeesity. 



THE small mounds OF THE UNITED STATES. 



In the two papers on the probable origin of 

 the small mounds in the southern and western 

 parts of the United States, which have ap- 



= L. c, p. 547. 



