AGRICULTUEAL BOTANY. 631 



The mycelium when thawed and kept at a temperature from 18 to 19° C. 

 showed no signs of life or plasmolysis, gave off no carbon dioxid, and stained 

 throughout with anilin dyes, but when the temperature was raised to from 

 30 to 34° the fungus developed rapidly, formed spores, and gave off carbon 

 dioxid gas very energetically. When the fungus was not subjected to the 

 optimum temperature of 30 to 34° after thawing, it soon died. 



It is claimed that in these experiments with the frozen Aspergillus mycelium 

 the boundary line between living and dead protoplasm has disappeared. 



Notes on intumescences in roots, H. V. Davis {Neiv PJnjtol., 9 {1910), No. 

 8-9, pp. 325, 3:26).— Previous investigations by Bayliss (E. S. R., 19, p. 527) 

 and others having shown that there is an abnormal elongation of cortical cells 

 following injuries to epidermal tissues, the author has undertaken to de- 

 termine the nature of the response on the part of roots. 



The primary roots of seedlings were injured by passing an electric current 

 through them in contact with platinum electrodes, by passing an electric cur- 

 rent through soil in which the seedlings were growing, by a spark from a coil 

 passed through the roots, by the application of acids and alkalis, and by burn- 

 ing with a hot glass rod. In all cases the seedlings were allowed to continue 

 growth in sawdust after the production of the injury. 



Sections showed that where the epidermal cells had been desti'oyed and a 

 scar formed, the uninjured cortical cells below the scar had elongated toward 

 it. The length of the hypertrophied. cells was found to be dependent on the 

 time allowed for their growth. 



In the experiments where roots were growing in a soil through which a cur- 

 rent was passed no intumescences were formed. This was believed to be due to 

 the fact that the current did not pass through the roots, since they offered a 

 greater resistance than the moist soil, and consequently there were no sudden 

 chemical or thermal changes in the root and no wound. For this reason, it is 

 believed that the electric stimulation acts as a traumatic stimulus. 



The effect of tarring roads on plants, M. Mirande {Gompt. Rend. Acad. Sci. 

 [Paris], 151 {1910), No. 21, pp. 9 ',9-952). —K study has been made of the in- 

 fluence of tarring roads on plants, not only in close proximity to the road, 

 where there might be some injury through the soil, but at a greater distance, 

 where the injury would be due to dust and vapors arising from the road. 



The author seems to think that the greatest injury is done through the 

 vapors which are given off in considerable abundance during dry, hot weather. 

 In this case the greatest injury would be to trees and plants along the border 

 of the road, in parks, or in closely settled regions, and less injury would be 

 observed in the open country. 



The author .states in conclusion that if trees and ornamental plantings 

 in cities are to be preserved, the use of tar on roads should be made with 

 care. 



The influence of tarring' roads on neighboring vegetation, E. Griffon 

 {Gompt. Rend. Acad. Sci. [Paris], 151 {1910), No. 23, pp. 1070-1013).— The 

 author states that laboratory experiments covering three seasons have con- 

 firmed the conclusion of Mirande (see above) regarding the injurious nature 

 of the gas given off from tar when used for coating roads, yet from extensive 

 observations he thinks the probable injury to vegetation in the open country 

 would be very small. 



A method of selection applicable to tropical agriculture, P. J. S. Cramer 

 {Ann. Jard. Bot. Buitenzorg, 1910, Sup. 3, pt. 1, pp. -^6^-472),— Attention is 

 called to the wide variability of indigenous plants in the Tropics, and various 

 methods of improvement selection are described. 



