June 2, 1916] 



SCIENCE 



785 



After wliicli, at the approach, of the dry sea- 

 son, and the discontinuance of the camp early 

 in May the numbers gradually lessened. 



So far as the incidental appearance of mala- 

 ria is concerned, while Major Ashburn says 

 the reports are perhaps unduly favorable, the 

 first case was sent into hospital February 7. 

 In December, shortly after the opening of the 

 camp it was inspected and malaria was pre- 

 dicted, but was not then present; in February 

 two cases were reported, by the last of March 

 the percentage on blood examination had risen 

 to 20 per cent., and in April to 100 per cent. 



It is to be noted that these Anophelines " did 

 not greatly abound until after the laborers had 

 been at this location for three weeks or more, 

 and malaria made no headway until after two 

 months." 



From these observations Major Ashburn 

 concludes, although for very different reasons 

 than the usual ones of ability in length of 

 flight, that " in ordinary sanitary practise, and 

 not considering such exceptionally large and 

 favorable breeding places, the control of all 

 breeding within four hundred yards of towns, 

 posts and houses serves to make them fairly 

 comfortable and safe residences."^ 



It is however the difference in reasons that 

 makes Major Ashburn's conclusions of especial 

 value, and the whole of Major Ashburn's paper 

 is well worth study. It throws an absolutely 

 new light on the subject, gives a valid reason 

 for the acknowledged limit of four hundred 

 yards as the usual flight of Anopheles, and 

 clears up some points in mosquito control that 

 have hitherto been obscure and bewildering. 

 C. S. Ludlow 



Army Medical Museum, 

 Washington, D. C, 

 May 4, 1916 



SPECIAL ARTICLES 



THE ORIGIN BY MUTATION OF THE ENDEMIC 

 PLANTS OF CEYLON 



In a recent paper Dr. J. C. Willis has made 

 a statistical study of the flora of Ceylon in 

 order to show that the indigenous species of 

 this island must have been developed by muta- 



3 Ashburn, P. M., ' ' Elements of Military Hy- 

 giene," 2d ed. (1915). 



tion and without any kind of advantageous 

 response to local conditions.^ 



It is obvious that the mutation theory wants 

 in the first place a study of those facts which 

 may throw a direct light on the evolution of 

 wild species and that only relatively young 

 forms have a sufficient chance of still living 

 under the same or almost the same conditions, 

 under which they originated. The material, 

 afforded by the flora of Ceylon, is exceptionally 

 rich in this respect and thoroughly well pre- 

 pared by numerous investigators and especially 

 in the great " Flora of Ceylon " by Trimen 

 and Hooker. 



Ceylon is a comparatively small island 

 (25,000 sq. miles) and has a flora of 2,809 spe- 

 cies of Angiosperms, of which 809 are endemic 

 to the island. 



Moreover of the 1,02Y genera to which those 

 species belong, 23 are confined to Ceylon, and 

 among the 149 families, this is the case with 

 six. Among the endemic genera 17 are repre- 

 sented by one species only, four by 2-3 and 

 only two by a large number. These latter are 

 Doona with 11 and Siemonoporus with 15 spe- 

 cies, almost all of which are very rare forms, 

 but distinguished from one another by char- 

 acters of full specific rank. They give the 

 impression that they may have been formed by 

 what Standfuss has called explosive methods, 

 a number of new species being produced almost 

 at the same time. 



As a rule, the endemic species are rare or 

 very rare. More than a hundred of them are 

 confined to one mountain top or to some very 

 small area in the mountains. 



Many of these occur as a very few individ- 

 uals, say a dozen or little more, and the places 

 where they can thrive are so small that it is 

 obvious that they can never have been much 

 more numerous. They must have evolved 

 on the spot where they are found. Notwith- 

 standing this, they are well-marked Linnean 

 species and accepted as such by Trimen and 

 Hooker. ISTot rarely their distinguishing char- 

 acters are relatively large. 



ij. C. Willis, "The Endemic Flora of Ceylon, 

 with Eeferenoe to Geographical Distribution and 

 Evolution in General, ' ' Phil. Trans. Roy. Soc. ' 

 London, Series B, Vol. 206, pp. 307-342. 



