262 EXPERIMENT STATION RECORD. 



germinating. The spores were found on dead leaves, straw, and on the partially 

 dead or green leaves of living grain or grasses. This also applies to a number of 

 other important rusts which attack wheat and allied grasses. 



In the case of Puctinia ruUgo-vera, it has been found wintering freely on living 

 leaves of wheat or winter rye, and upon the matured leaves and straw of the same, 

 from Mississippi to North Dakota. 



Report on the root-rot investigations, Z. Kamerling ( Verslag van het wortelrot 

 onderzoek. Soerabaya: II. van Ingen, 1903, pp. 209, pis. 5).— The author reports on 

 the various studies he has made to determine the cause of root rot of sugar cane. 



The physical structure of the soil has been found to be one important cause, and 

 physically poor soils are defined as those on which the cane develops poorly or dies 

 prematurely. Such soils have a very close structure, the grains of less than T V mm. 

 being all distinct and separate from each other. Better soils are those in which few 

 or many of these small grains adhere in masses, forming a more open structure. In 

 the latter case the soil particles may be stuck together either by humates, by iron 

 hydroxids, or by iron silicates. The structure of the soil may be improved by the 

 addition of river silt, by cultivation, and by irrigation. 



Soils which are in poor physical condition become closely packed, so that they are 

 poorly aerated and hard, making it difficult for the cane roots to penetrate. This 

 condition causes malformation of roots as well as stunted growth. Measurements of 

 cane roots made from plants growing in especially prepared soils showed that the 

 volume of soil penetrated by roots growing in soil of good physical structure wai 

 eighteen times as great as the volume of soil penetrated by cane roots growing 

 soil of poor physical structure. 



A number of tests were also made on the relative permeability of soils to water, 

 and it w T as found that the soils in which the root rot occurred were much less 

 permeable than other soils. The details of the results of these experiments are 

 illustrated by several diagrams. 



Poor physical structure of the soil is partly due to loss of humus, which loss, the 

 writer finds, amounts in 3 years to 0.09 per cent for the upper foot of soil. This loss 

 can be made up by adding organic fertilizers in the shape of stable manure with which 

 rice straw, cane leaves, and other organic substances have been composted, or by 

 turning under green plants. 



In regard to the presence of root parasites the author expresses the opinion that 

 on otherwise healthy plants the presence of parasites is no very serious matter. It is 

 only when, by reason of poor soil conditions, the plants are weak that parasites are 

 able to do much damage. 



A nematode, Heterodera radicicola, and several kinds of fungi which occur more or 

 less frequently are described. — h. m. pieters. 



Smut preventives and their effect on the germination of grain, R. W. Pea- 

 cock (Agr. Gaz. X. S. Wales, 16 {1905), Xo. 3, pp. 251, 252).— The author tested the 

 effect of solutions of copper sulphate and formalin in various strengths, and the hot- 

 water method of seed treatment, for the prevention of smut to determine the possible 

 effect on germination. 



In dry districts the use of copper sulphate in solutions of ordinary strength was 

 attended with a loss of 50 per cent of the grain. Formalin was found to be prefer- 

 able under unfavorable conditions, and the hot-water treatment was decidedly effi- 

 cacious but can only be recommended to careful operators on account of the narrow 

 limits within which the temperature must be kept. 



Disease-resistant potatoes, W. Stuart ( Vermont Sta. Bid. 115, pp. 135-140) . — 

 The author has been engaged for 2 years in studying the varying resistance of varie- 

 ties of potatoes to disease, particularly the late blight (Phytophthora infes'ans). 



Of the varieties tested in 1903 one, which is designated as Rust Pi oof, proved quite 

 resistant to the disease. In 1904 a more extended list of varieties of potatoes together 



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