188 BOTANICAL GAZETTE [FEBRUARY 
with 43 species, the composites with 42 species, the grasses with 55 species, the 
euphorbias with 7 species, and the orchids with 11 species.—GE0. D. FULLER. 
Cuscuta and its host.— Investigating the relations existing between certain 
species of Cuscuta and various hosts, particularly with regard to the connection 
established between the phloem of parasite and that of the host, THopayY’s 
concludes that the cell walls of the haustorial phloem degenerate, and are 
absorbed at the point of contact with the sieve plates of the host, and the naked 
protoplasm of the parasite applies itself to the sieve area of the host. No 
connecting threads of protoplasm are found, and the translocation of food 
substances appears to be by a passive filtration of the contents of the sieve 
tubes of the host, forced by internal pressure, escaping into the parasite. 
This and other evidence favors the conclusion that connecting threads of ~ 
protoplasm occur only between genetically connected cells. The interpreta- 
tion of the results contains glaring examples of teleology, as we are assure 
“that the parasite takes much trouble to make use of the host sieve fields as 
they are, and not to disturb the mechanics of the sieve tubes’’!—Geo. D. 
FULLER. 
The prairies.—Studying the prairies of Iowa, SHmmeK” concludes that 
they were originally covered with floras of six more or less distinct types, and 
gives lists of species for each. He reviews carefully the various theories as 
to the factors causing their development, and gives a rather extensive bibli- 
ography of the origin of this type of vegetation, with brief notes on many of 
the titles. His principal contribution consists in attempts to obtain quantita- 
tive determinations of certain of the factors which may have been efficient in 
causing prairie development. Conspicuous among the data obtained are 
those of the comparative rates of evaporation at prairie and forest stations of 
observation. These data, although very scanty, seem to be significant, and 
lead to the conculsion that “exposure to evaporation as determined by tempera- 
ture, wind, and topography is the primary cause of the treelessness of the 
prairies.””—Gro. D. FULLER. 
%s THopAY, Mary G. (Sykes), On the histological relations between Cuscula 
and its host. Ann. Botany 35: 655-082. 1911. 
16 SyiMEK, B., The prairies. State Univ. Iowa, Lab. Nat. Hist. Bull. 61 :69-24°- 
pls. 13. 191I. 
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