620 ETPEKOTENT STATION EECOBD. [Tol. 37 



bracing the greater part of the remaining area within the Tropic of Capricorn ; 

 and (3) temperate climates — that is, practically those of the four southern 

 States of Brazil, beginning on the coast with Santos, just outside of the 

 Tropic, but extending in the higher interior 2 or 3 degrees north of that line. 

 These gi'oups are then subdivided into regions in accordance with the rainfall 

 and humidity, altitude, and situation with respect to the ocean, and under 

 each of these the climates of minor regions are studied with reference to 

 selected typical stations. The first group is divided into the superhumid or 

 Amazonian type, and the semiarid or northeast Brazilian type; the second, 

 into the semlhumid type of the middle latitudes, and the semihumid altitude 

 type." 



It is stated that droughts are more often due to irregular and badly dis- 

 tributed rainfall than to actual deficiency. One of the peculiarities of farm- 

 ing in the drier areas of northeastern Braizil is the use of artificial reservoirs 

 (agudes) "dotted over the surface, not for the supply of irrigation water to 

 be led to adjacent fields, but merely to allow of*the marginal tracts of silt 

 es^posed after floods being cultivated during the dry season. The topography 

 of large parts of this region is such that the lowering of the water surface In 

 one of these reservoirs by the evaporation of 5 ft. in depth of water is enough 

 to expose immense tracts of cultivable ooze." 



The weather conditions, especially distribution of the rainfall, of the plateau 

 of Sao Paulo are peculiarly suited to the growth of coffee. The fact that 

 Brazilian coffee has suffered so little comparatively from diseases Is attribu- 

 table to the favorable weather conditions. 



As regards cacao, humidity is a more Important climatic requirement than 

 temperature, since this plant Is especially susceptible to Injury from drought. 



It is noted that among the essential climatic requirements for sugar cane 

 is an abundance of rain. In the Campos region, where sugar cane is princi- 

 pally grown, there is sufticient rainfall during two or three months to make 

 conditions exceptionally favorable for the growth of this crop. There are, 

 however, occasional dry years, which are seriously injurious unless irrigation 

 is freely practiced. The irregularity of the precipitation in this region Ls 

 shown by the fact that during the 20 years, ISSS to 1907, the total annual 

 rainfall varied from 8 to 95 in. 



Fro.sts are very irregular in occurrence and distribution and do not form a 

 constant phenomenon at any given place. 



A classified bibliography Is given. 



The rainfall regime of Indo China, G. Le Cadet {Bui. ^con. Indochina, n. 

 ser., 20 (1917), No. 12S, pp. ISO. pis. 4). — Tables and charts are given which 

 show the mean rainfall and number of rain daj-s per month and per year, as 

 well as the extremes of such data, at stations well distributed throughout the 

 country, for periods varying from five to ten years. The characteristic features 

 of the rainfall of the region as shown by the data are discussed, as well as cer- 

 tain features of the relation of the amount and distribution of rainfall to plant 

 growth. 



The average annual rainfall shown by the data reported appears to be about 

 1,800 mm., varying widely, however, in different years and localities. The num- 

 ber of rain days averages over 100. Attention is called especially to the greater 

 plant response to freshly fallen rain due to Its higher radioactivity. 



Dissolved oxygen in rain water, E. H. Richakds (Jour. Agr. Sci. [England], 

 8 (1917), No. 3, pp. SS1-S37, figs. t). — Reference Is made to the importance of 

 dissolved oxygen in rain water as one of the chief factors controlling bacterial 

 activity In soil, particularly In relation to the decompo.sition of organic matter. 

 Previous investigations on the subject are briefly reviewed, and the results of a 



