424 BOTANICAL GAZETTE [may 



while another 20 per cent are found also in the Pacific mountains, leaving 60 

 per cent peculiar to the Rockies. Of these, fully one-half are restricted to the 

 southern Rockies, and less than one-fourth to the northern Rockies. Of the 

 locally endemic species, which are all herbaceous, 6 are confined to the Cana- 

 dian Rockies, 3 to Montana, 3 to Idaho, 14 to Wyoming, 13 to Utah, and 16 to 

 Colorado. Viola biflora is noted as having the most remarkable distribution, 

 having been found only in a few places in Colorado, in Alaska, and in Europe. — 



Geo. D. Fuller. 



A polycotyledonous bean. — Harris 26 has secured a race of the common 

 garden bean which shows steadily more than 2 cotyledons as tested by 3 off- 

 spring generations, comprising thousands of individuals. Since the race appears 

 in a "pure line'' and has remained constant in several differential features, 

 he concludes that its origin and behavior are characteristic of mutation as 

 defined by DeVries. The cotyledons are highly variable in number, ranging 

 from 2 to 7, but have a modal frequency of 4. For this reason the embryo 

 is described as tetracotyledonous. This persistent tendency of a dicotyle- 

 donous type to develop polycotyledony is an interesting confirmation of the 

 claim that the number of cotyledons developed depends upon conditions rather 

 than upon inevitable inheritance. — J. M. C. 



Illinois Academy. — The volume of Transactions of the Illinois Academy 

 of Science for 191 5 has just appeared. It contains the following botanical 

 papers: Comparison of a Rocky Mountain grassland with the prairie of 

 Illinois, by George D. Fuller; Studies in Phyllosticta and Cercospera, by 

 Esther Young; Method of prophesying the life duration of seed, by James 

 E. Groves; Peculiar examples of plant distribution, by H. S. Pepoon; The 

 grass flora of Illinois, by Edna Mosher; A Florida smut, Ustilago sieglingiae, 

 in Illinois, by Margaret Mehlhop. A symposium on colloids includes the 

 following papers: Outline of the chemistry of colloids, by D. A. MacIxnes; 

 Significance of colloidal chemistry in physiology, by William Crocker. — 

 J. M. C. 



Bog theories. — The vegetation of peat bogs exhibits such remarkable 

 peculiarities of habit and structure that it has called forth a number of varied 

 and somewhat conflicting explanatory theories. These theories have been 

 summarized carefully by Rigg, 27 especially in so far as the xerophily of the 

 plants is concerned, in a manner that is likely to prove very useful. A good 

 bibliography adds to the value of the paper. — Geo. D. Fuller. 



^Harris, J. Arthur, A tetracotyledonous race of Phaseolns vulgaris. Mem 

 N.Y. Bot. Gard. 6:229-244. 1916. 



27 Rigg, G. B., A summary of bog theories. Plant World 19:310-325. 1916. 



