338 



SCIENCE 



[N. S. Vol. XXXVII. No. 948 



Helichrysum, 59; Senecio, 36; Aster, 3; with 

 no Solidago, and no Helianthus). 



Of trees there are many species, but nearly- 

 all belong to genera unfamiliar to northern 

 readers. Thus while there are two willows 

 {Salix), one Celtis and 13 species of Ficus, 

 there is no Pinus, Picea, Abies, TJlmus, Frax- 

 iniLS, Acer, Juglans, Quercus, Fagus, Cas- 

 tanea, Betula or Alnus. 



The authors are to be congratulated upon 

 having brought out so creditable a list of the 

 plants of their country, and we may express 

 the hope of the botanists of the northern 

 hemisphere that they will be encouraged to 

 follow it soon with a descriptive manual. 



Greene's " caeolus linnaeus " 

 At the Linnaean bicentenary memorial ex- 

 ercises held in Washington Dr. Edward Lee 

 Greene gave a notable address (now issued in 

 a little book of 91 pages by the Cower Com- 

 pany of Philadelphia) in which he discussed 

 with rare perspicacity and scientific sympathy 

 the life of " the matchless Swede," Linnaeus. 

 In it he discussed the lineage and childhood 

 of Linnaeus, his school, college and university 

 years; his journey to Lapland; journey to 

 Germany and Holland; his practise of medi- 

 cine in Stockholm; appointment to be a pro- 

 fessor at Upsala, and his influence upon bot- 

 any. Under the last head Dr. Greene says : 



It will be difficult to bring the average botanist 

 of to-day to a realization of how great an epoch 

 in botany Linnaeus created when he began exam- 

 ining the stamens of every plant, with the purpose 

 of ascertaining into what one of his twenty-four 

 proposed classes of flowering plants each generic 

 tjTJe must fall. And though it be true that the 

 classes and orders of Linnaeus fell into disuse 

 three quarters of a century ago, it is true to-day 

 that every botanist, from the mere beginner in 

 taxonomy to the most accomplished master of it, 

 if he have a new and unknown plant in hand for 

 determination, makes his final appeal to stamens 

 and pistils. ... In this procedure every botanist 

 who lives is distinctly a disciple of Linnaeus. 



The last chapter of the little book, on Lin- 

 naeus as an evolutionist, was prepared two 

 years later (1909) and brings out the fact 



that the great botanist was by no means the 

 believer in the " fixity of species " that we 

 have been led to believe. After quoting from 

 the " Philosophia Botanica " which " excludes 

 every idea of a possibly evolutionary origin 

 for any species of plant," Dr. Greene says : 

 " And yet, Linnaeus was an evolutionist," and 

 proceeds to quote later statements which indi- 

 cate that as the years went on he came to the 

 view that some species may have been derived 

 from preceding species. 



The book should be in the hands of every 

 teacher of botany, and we may add zoology, 

 also, since there is a short but very suggestive 

 chapter by Dr. Wm. H. Dall on Linnaeus as 

 a zoologist. Charles E. Bessey 



The University of Nebraska 



SPECIAL ARTICLES 



MAGMATIC DIFFERENTIATION AT SILVERBELL, ARIZ. 



In the course of a study of the ore-deposits 

 of Silverbell, Pima County, Ariz., some inter- 

 esting facts bearing upon magmatic differen- 

 tiation were noted. A detailed description of 

 this district has been published,' but as that 

 paper is largely devoted to problems in eco- 

 nomic geology, it seems advisable to summarize 

 here the facts of interest to petrologists. The 

 region described consists of a complex of late 

 Jlesozoic or early Tertiary intrusives entirely 

 surrounding detached blocks of highly meta- 

 morphosed limestone. The igneous rocks in 

 the order of intrusion are (1) alaskite, (2) 

 alaskite porphyry, (3) granite, and biotite 

 granite porphyry, and (4) quartz porphyry 

 (dacite porphyry?). Many complex flows of 

 basic composition are found just outside the 

 area studied. The chief problem is the origin 

 of the biotite granite, which is believed to 

 represent a differentiation product of the 

 magma from which the alaskites came. 



The alaskite is a light gray rock, consisting 

 almost entirely of quartz and orthoclase, the 

 grains averaging about a half a centimeter in 

 diameter. It contains a little plagioclase, and 

 very rarely shows biotite or hornblende. It is 

 bounded on one side by the later intrusion of 



'^ Bull. Amer. Inst. Min. Eng., May, 1912, pp. 

 455-507. 



