72 



SCIENCE 



[N. S. Vol. XL VII. No. 1203 



read that " with, only one exception, each 

 group of islands has its own characteristic 

 •pecies which occur nowhere else. 



"The same correlation between geograph- 

 ical and specific discontinuity is displayed by 

 the species of the different islands of one and 

 the same group for each member possesses 

 distinct species not found in the others " (p. 

 11) ; and that the various varieties are con- 

 fined within rather easily definable geographic 

 limits. 



It would seem that the isolation factor had 

 been so taken for granted as to be overlooked. 

 It has certainly not been the only, perhaps 

 not a necessary, factor. For instance (p. 309), 

 we find mention of " two absolutely independ- 

 ent varieties [of P. otaheitana], rubescens 

 and affinis, which have almost identical geo- 

 graphical limits; yet they stand in the sharp- 

 est possible contrast to one another." A very 

 intensive study of these two varieties would, 

 in the reviewer's opinion, almost surely show 

 some slight difference of habit, of adaptation 

 to the same environment, otherwise being too 

 far separate to interbreed freely, one of them 

 should have crowded the other out. 



Perhaps, the conclusion of the widest in- 

 terest, if not of the greatest importance, is 

 found in the following statement. "The evi- 

 dence tends to prove that the dominant geo- 

 logical process in South Pacific regions has 

 been one of subsidence, which has progres- 

 sively isolated various mountain ranges pre- 

 viously connected, so that they have become 

 separate island-masses, which, in their turn, 

 have been subsequently converted into the 

 disconnected islands of the several groups." 

 John T. ISTichols 



American Museum of Natural Histort, 

 New York 



SPECIAL ARTICLES 



FURTHER EVIDENCE RELATIVE TO THE 



VARIETAL RESISTANCE OF PEANUTS TO 



SCLEROTIUM ROLFSII 



During 1916 data were collected^ which indi- 

 cated that there is a marked difference in the 



1 McClintock, J. A., ' ' Peanut-wilt caused by 

 Sclerotium Solfsii," Journal of Agricultural Be- 



susceptibility of peanut varieties to the at- 

 tacks of Sclerotium Bolfsii. 



The soil in the plots where the peanut 

 rotation experiment is being conducted has 

 been proven to be thoroughly infested with 

 Sclerotium Bolfsii, and the Valencia variety 

 has shown great susceptibility to the attacks 

 of this fungus; therefore, at the writer's sug- 

 gestion, the use of the Valencia variety for 

 the rotation experiment was discontinued, and 

 commercial seed of the Virginia Bunch vari- 

 ety was substituted for use in 1917. Plots one 

 and three, each about one third of an acre in 

 size, were planted for the 1917 test. Plot one 

 had grown peanuts continuously since 1910, 

 while plot three had grown peanuts in 1911 

 and 1914. 



It was observed that some of the supposed 

 Virginia Bunch plants had a procumbent 

 habit of growth, and when these plants began 

 to blossom the suspicion that they were of the 

 Virginia Runner variety was confirmed. As 

 these two varieties are supposed to be merely 

 selections of erect and procumbent types of 

 plants from the same original variety, the 

 presence of the Virginia Runner plants in the 

 1917 plantings might be due either to a slight 

 mixture of the commercial seed, or a failure 

 of the Virginia Bunch variety to be in all 

 cases well fixed. 



The two plots were under observation until 

 the crop was harvested, ISTovember 9, 1917. 

 During this time the writer found one Vir- 

 ginia Bunch plant in each plot which had 

 wilted, and examination disclosed the coarse, 

 white mycelium of Scelerotium Bolfsii about 

 the base of the stems, thus indicating that the 

 wilting was due to this fungus, as had been 

 proven in many cases in 1916. 



The fact that none of the Virginia Runner 

 plants wilted confirms the data collected in 

 1916 to the effect that this variety is practi- 

 cally immune to the attacks of Sclerotium 

 Bolfsii. 



The resistance of the Virginia Bunch va- 

 riety in 1917 was much greater than in 1916, 

 as shown by the fact that in 1916, out of a 



search, Vol. VIII., No. 12, pp. 441-448, March 19, 

 1917. 



