1918] CURRENT LITERATURE 360 
- of considerable significance to agriculture that the addition of fertilizers does 
not increase the susceptibility of the grains to rust infection. High moisture 
content of the soil was favorable for rust development. Slope and drainage 
consequently had an influence only in so far as the soil moisture content was 
affected thereby. 
A more direct attack upon the problem of the influence of environmental 
factors on the development of rusts was undertaken by Matns.4 In his work 
the effect on Puccinia coronata and P. Sorghi of a number of factors, partly 
external and partly internal to the host, was studied under controlled condi- 
tions. It was found that low temperatures (13-15°) retard the development of 
these rusts, and that there is also an upper limit in the neighborhood of 30° 
beyond which growth of the parasite does not take place. Both wet soil and a 
saturated atmosphere favor the development of rusts, to the highest degree 
when both factors are present simultaneously. Absence of any of the mineral 
elements necessary for plant growth does not prevent infection, but decreases 
the number of pustules produced. The light relations are of special interest 
as giving an indication of the mode of nutrition of rusts. Light as such is not 
necessary for the development of the parasite; if, however, the host has been 
depleted of carbohydrates by being kept in the dark, no rust development takes 
place. Light, therefore, acts indirectly in so far as it is necessary for the pro- 
duction of carbohydrates for the nourishment of the fungus. For the same 
reason, rust does not develop in the absence of carbon dioxide on plants which 
have been deprived of carbohydrates. Puccinia Sorghi develops in the dark 
In continuation of his observations on the wintering of rust fungi, TRE- 
BOUXS reports a number of cases in the vicinity of Riga of the hibernation of 
rusts by means of a persistent mycelium. The observations were made in 
February, March, and April, when the melting snow had >. the host 
plants, and before infection from external sources had been possi 
the host plants were brought into a warm room further en of 
unopened sori was observed in Puccinia dispersa on Secale cereale and 5. 
on A gropyrum repens; Uredo Airae on Aira caespitosa; and Thecopsora Pirolae 
on Pirola rotundifolia.. In addition to these, field observation showed the 
4M B., The relation of some rusts to the physiology of their hosts. 
Amer. Jour. Bot. 4:179-220. stir 2. 191 
5’ TrEBoux, O., Uberwintering scaiaioeabe Mycels bei einigen parasitischen 
Pilzen. Mycel. Ceatealls. §:120-126. 1914 
