96 THE PLANT WORLD. 



facts it is plain that agencies now in operation are amply snfR- 

 cient to account for the occurrence of certain species of plants in 

 regions as remote as Argentina and tlie Rocky Mountain country. 



A remarhahle case of foliage orientation occurs in tlie Mex- 

 ican greasewood, CoviUea mexicana, the causes of which are 

 quite obscure. It should be noted that the branches show a dis- 

 tinct dorsiventrality, readily observable, so that a typical branch, 

 leaves and all, lies in a single plane, broadly speaking. In 

 addition to this, however, there is a placing of the branches so 

 that their upper surfaces all face the southeast. It is true that 

 many individual plants, due to disturbing causes, do not display 

 this behavior in a marked degree. On the other hand a careful 

 examination will discover the orientation where at first it does 

 not seem to be present, and the very great majority of plants 

 show it readily. I have not been able to detect that position 

 with respect to the topography affects the matter, and the con- 

 stancy of the attitude of the branches on larc-e areas of the 

 mesa certainly calls for explanation. F. E. Ll. 



The annual session of lite Biological Lahoratorij of the 

 Brooklyn Institute of Arts and Sciences, at Cold Spring Har- 

 bor, L. I., will last this summer from July 3 to August 17. The 

 course in Cryptogamic Botany will be conducted by Prof. Dun- 

 can S. Johnson, of Johns Hopkins University, aided by jMr. 

 Harlan H. York of the University of Texas. The course in 

 Plant Ecology will be given by Dr. E. ]Sr. Transeau, of the Sta- 

 tion for Experimental Evolution, assisted by Mr. W. C. Cooper, 

 of Johns Hopkins University. As usual, assistance will be 

 given to all those wishing to do advanced botanical work in either 

 of the lines mentioned. Botanists prepared to take up inde- 

 pendent investigation may secure private rooms in the research 

 laboratory by communicating with the Director of the Labora- 

 tory, Cold Spring Harbor, L. I., I^T. Y. 



Wanted to Exchange or Buy — Back numbers of The Mi- 

 croscope and also of The American Journal of Microscopy. 

 Address Morton I^icholson, 1012 S. 4th St., Tacoma, Wash. 



