139 



^ iu^ v,iu.c.^..i^a,i.iv^li iiiijj. 



now be of great interest to secure satisfactory specimens of this 

 plant, in order that the doubt concerning its classification might 

 be set at rest. 



Announcement of the A. A. A. S. Committee on a Botanical Exchange. 



7b the Members of the Botanical Club of the A. A. A, S. : 



Vour committee, appointed in August last to devise a method for the exchange ^f 

 specimens among American botanists, have, after consultation with other botanists, 

 decided that the most practical method is through the herbarium of the Department 

 I of Agriculture, at Washington. 



^ A classified stock of duplicates belonging to the Department is available as a 

 basis of an exchange herbarium. 



I hose desiring to exchange specimens iihould address, for rules and other infor- 

 mation, Dr. Geo. Vasey, U. S. Department of Agriculture, Washingloii, D. C, 



Geo. Vasey, N. L. Britton, 



. Sereno Watson, B. D. Halsted, 



r 



Thomas Morong, Committee. 



Reviews of Foreign Literature. 



i^xpenmeutelle Unterstichunz Hber das Wachsthinn der Zellmem- 



bran. By F. Noll. (Abhandlung der Senckenbergerischen 



Naturforschenden Gesellschaft, Bd. xv, 1887.) 

 A short review of this paper, describing some interesting ex- 

 periments in respect to the manner of growth of cell membrane, 

 IS given in the Centralblatt, Vol. H, No. 4, 1888. The follow- 

 ing is a brief abstract of the review : 



The author first gives a historical sketch of the opinions held, 

 at different times, of the manner of growth of the cell membrane. 

 The first generally adopted theory w^as that of growth by apposi- 

 tion. Naegeli, in his work on starch grains, almost entirely over- 

 threw this theory, establishing m its place that of intussusception. 

 Gradually doubts arose regarding this mode of growth and the 

 <^Pposition theory gained new adherents, until at the present 

 time the two theories stand opposed to each other, and the ques- 

 tion is left for future investigators to decide. 



The author undertakes to solve the question experimentally, 

 by causing a difference in color between the old and new growth 

 ^^ membrane. As the new membrane will not take up aniline 

 ^r similar coloring stuff, the old membrane w^as colored and the 

 new left colorless. The method used has already been success- 

 ful in solving questions in animal physiology. Living specimens 



