DISEASES OF PLANTS. 243 



Attempts have been made to grow these plants in a greenhouse, and suc- 

 cessful results were obtained when they were transplanted without breaking 

 the roots of the parasite attached to those of the host, or when they were 

 germinated in the presence of the roots of the host plants after the seed had 

 been exposed to freezing temperatures. 



It is stated that Meinecke found that seeds sown in 1913 remained dormant 

 until 1915, when they germinated and grew without attachment to host plants. 

 This indicates that species of Comandra can live without parasitism if neces- 

 sary, but it remains to be seen whether these plants will continue to grow 

 indefinitely without the presence of host plants. 



The effects of illuminating gas on root systems, E. M. Haevey and R. C. 

 Rose (Bot. Gaz., 60 {1915), No. 1, pp. Zl-kh, figs. 9).— This investigation was 

 undertaken to determine some of the effects of illuminating gas on root sys- 

 tems, in order to secure further diagnostic characters of gas poisoning and to 

 ascertain whether the chief causes of gas injury are the soluble constituents or 

 the relatively insoluble ones which are found mainly in the interstices of the 

 soil. 



Tests are described in which it is claimed that the odorous constituents of 

 gas, which are slightly or not at all toxic to roots of plants, were readily 

 absorbed and strongly held by the soil. The constituents remaining in the 

 gaseous state thus constituted the chief source of injury to root systems. 

 Ethylene is probably the most harmful of the constituents, except in very high 

 concentrations of illuminating gas, in which case other substances and other 

 factors may become operative. 



High concentrations of illuminating gas resulted in rapid killing, with devel- 

 opment of no other symptoms. Low concentrations of ethylene gas, or of 

 illuminating gas having like concentrations thereof, caused abnormal develop- 

 ment of tissue, from 2.5 to 20 per cent of illuminating gas producing this effect 

 within 8 to 21 days. 



Abnormal tissue development in the roots of woody plants often followed 

 slow percolation of gas through the soil. In low concentrations of illuminating 

 gas, hydrolysis of starch and some related chemical reactions were accelerated. 



The etiolated sweet pea seedling is said to be a very delicate indicator of 

 illuminating gas in the soil. 



A bibliography is appended. 



The fungicidal and insecticidal action of hot water and hot coppei* sprays, 

 L. Semichon {Conipt. Rend. Acad. Agr. France, 1 {1915), No. 5, pp. 190-206). — 

 It is stated that while the tissues of fruit trees and garden plants undex'go 

 without injury spraying for a few seconds with water at a temperature of about 

 65 to 75° 0. (149 to 167° F.), some of their common cryptogamic parasites are 

 checked by spraying at 55 to 65° C. (131 to 149° F.), and these temperatures 

 are also fatal to injurious insects. 



These temperatures are said to confer increased capacity to spread, penetrate 

 interstices, and adhere in case of copper sprays. The cost of treatment and 

 possible adaptations thereof are also discussed. 



Mildew of cereals (Sclerospora macrospora) in France, G. Aenaud {Compt. 

 Rend. Acad. Agr. France, 1 {1915), No. 14, pp. 429-435, figs. 2). — The presence 

 of 8. macrospora on wheat is noted, supposedly its first appearance in France, 

 though not uncommon in parts of Italy, where other plants, cultivated or wild, 

 are also attacked. 



The fungus appears to develop most favorably in moist localities, attacking 

 all aerial portions of the plant, but more commonly the leaf. It may cause 

 deformation, discoloration, and desiccation, the damage done to crops, however, 

 appearing to be comparatively small, except in very humid localities. 



