26 EXPEEIMENT STATION RECORD. 



well adapted for their cultivation. Manure, straw, and trash also furnish 

 effective protection when spread upon the land uniformly. " More extreme 

 measures must be taken with [sandy soils], such as farming in strips, [and] 

 allowing weeds or other vegetation to grow and form windbreaks on the 

 alternate strips." 



Contribution to the physiology of soil, Bernbeck (Forstw. Centbl., n. ser., 

 86 (1914), No. 1, pp. 26-44). — This article discusses the importance of the 

 " physiological depth " of soils, i. e., the depth of the soil layer in which roots 

 grow, particularly in its relation to the free circulation of moist air in forest 

 soils. Various means of increasing the physiological depth are described. 



The distribution of bacteria in various soil types, H. J. Conn (Jour. Amer. 

 ^oc. Agron., 5 (1914), No. 4, PP- 218-221). — The results of studies of the micro- 

 flora of 14 dfferent soils make "it evident that, both quantitatively and quali- 

 tatively, there is surprisingly little variation between the bacteria of different 

 soils. Soil has its own distinctive types of bacteria, and they are not many in 

 number." The predominating types observed in cultures in ordinary media, 

 and not including nitrifying, nitrogen-fixing, and other forms, were as follows: 

 (1) Peritrichic, spore-bearing, long rods (5 per cent) — BaciUtis mycoidcs, B. 

 suMilis, B. megatherium, and an imnamed type; (2) nonspore-bearing, short 

 rods (50 per cent) — liquefying type (unnamed), and nouliquefying tjrpe 

 (unnamed) ; (3) Pseudomonas (5 per cent) — P. fluorescens (liquefying), and 

 nouliquefying type (unnamed) ; (4) Actinomycetes (40 per cent) — A. chro- 

 mogcnus ( ?) and A. albus. 



" In every soil studied, whether a muck, a clay loam, a loam, or a sand, all 

 of these types were found and no others occurred in appreciable numbers." 



Real and apparent nitrifying powers, P. L. Gainey {Science, n. ser., 39 

 {1914), No. 992, pp. 35-31; ahs. in Chem. Ahs., 8 {1914), No. 5, p. 978).— Data 

 are presented to show that deducting the nitrate nitrogen originally present or 

 that in an incubated check as is done in two of the methods commonly used to 

 determine the nitrifying power or efficiency of soils does not give correct results 

 when easily decomposable organic nitrogenous substances are added to soils 

 containing nitrate nitrogen. 



" Simply taking as the correct factor the amount found at the final analysis 

 will probably approach nearer the truth than any other method now in prac- 

 tice." However, this method gives only the apparent nitrifying power of the 

 soil since " there is absolutely no way of determining the actual amount 

 formed that immediately disappears." 



Studies on soil protozoa, A. Cunningham and F. Lohnis {Centbl. Bakt. 

 [etc.}, 2. AM., 39 {1914), No. 23-25, pp. 596-610) .—The investigations reported 

 dealt with the growth of protozoa on various media and the effect of heat on 

 active and encysted forms. 



The death point of active and encysted protozoa was found to be for flagel- 

 lates 44° C. (active forms), 70-72° (cysts); for ciliates 54° (active forms), 

 72 (cysts) ; and for amoebie 48° (active forms), 72° (cysts). 



" In the case of the cysts the figures obtained are quite constant for the three 

 forms of protozoa examined. The active forms, however, show marked dif- 

 fei-ences in their power of resistance and it is noteworthy that the latter appears 

 to be roughly in proportion to the average size of the individuals. 



" The results show quite a marked difference between the powers of resist- 

 ance to heat of the cysts and the active organisms — a difference at all events 

 quite large enough to allow of the selection of an intermediate temperature 

 which will kill all active forms but leave the cysts uninjured. In the fixing of 

 this temperature, however, the retarding effect which heat has had upon 

 excystation in these experiments must be kept in mind. It will, therefore, be 



