Floristik, Geographie, Systematik etc. 379 



reviewed. This part deals with the Vegetation of rock ravines, river 

 and stream bluffs and flood plains, with mention of the principal 

 species, Harshberger. 



Ramaley, F., Dr}^ Grassland of a High Mountain Park in 

 Northern Colorado. (The Plant World. XIX. p. 249— 270. Sept. 

 1916.) 



This is an intensive study of the dry grassland of a mountain 

 park in northern Colorado at an altitude of about 9000 feet. The 

 Vegetation is described as lovv-growing, consisting largely of grasses 

 and sedges with many profusely-flowering perennials. Five seasonal 

 periods are recognized. A brief section on environmental factors 

 discusses climate, soil, evaporation, importance of ground squir- 

 rels, etc. Accounts are presented of geography, duration of indi- 

 viduals and Underground parts of plants. A list of 13 plants is given. 



Harshberger. 



fej^ 



Rigg , G. B., A Summary ofßogTheories. (The Plant World. 

 XIX. p. 310—325. Oct. 1916.) 



In this paper the writer has arranged systematically the various 

 theories which have been offered in explanation of the fact that 

 plants other than bog xerophytes are largely inhibited from sphag- 

 num bogs. The principal papers on this subject are discussed and 

 a copious bibliograph\^ is given. Harshberger. 



Shimek, B., The Plant Geography of the Lake Okoboji 

 Region. (Bull. Lab. Nat. Hist. State Univ. of Iowa. VII. p. 3-90. 

 8 pl. 1 plate map. I9I9.) 



The paper opens with an account of previous work, then treats 

 of the physiography and drainage and of the ecologic regions which 

 include the prairie (for which climatic conditions are given), swamps, 

 lakes and forest with a tabular arrangement of the species for each 

 region. A bibliography is given. Harshberger. 



Shimek, B., The Prairies. (Bull. Lab. Nat. Hist. State Univ. 

 Iowa. VI. p. 169-240. 13 pl. and 1 map plate. April 1911.) 



Shimek believes that exposure to evaporation as determined by 

 temperature, wind and topography is the primary cause of the 

 treelessness of prairies and that the prairie flora persists on the 

 exposed areas because it is xerophytic. Rainfall and drainage, 

 while of importance, because determining the available supply of 

 water in both soil and air, are not a general, determining cause, 

 both frequently being equal on contiguous forested and prairie 

 areas. Solls and geologic formations are of value only in so far as 

 the}^ affect conservation of water; the porosity of the former deter- 

 mining its power of holding moisture, and the latter often deter- 

 mining topography. Prairie fires were an effect rather than a 

 cause, and where acting as a cause were local. Seed dispersal 

 probably largely accounts for the grouping of plant societies on the 

 prairies, but does not account for the presence of the prairie flora 

 as a whole. Harshberger. 



