810 EXPERIMENT STATION RECORD. 



The correlation of growth under the influence of injuries, 

 C. O. TowNSEND (Ann. Bot., 11 (1897), No. 44, pp. 509-532).— The author 

 has reported on a series of experiments to test the first effects of injury 

 upon the growth of plants, to determine the effect of a single irritation 

 of short duration, and the time required for such an effect to manifest 

 itself. The well-known effect of the removal of the branches of a tree 

 on the development of other branches or the development of fruit and 

 the disturbance of the roots of garden plants through cultivation are 

 mentioned. The experiments for the most part were conducted with 

 seedlings of Phascolus multiflorus,Vicia faba, Lupinus albus, Helianthus 

 annuus, Cucurbita pepo, Zea mays, Arena sativa, Hordeum vulyare, and 

 Secale cereale; also with older plants of Calla and a few cuttings of 

 willows. A number of experiments were also made with Phycomyces 

 nitens. The different experiments are reported upon in detail, and the 

 following summary is given: 



"A single irritation produced by cutting or splitting the shoots or roots or 

 removing the leaf tips of seedlings tends to produce a change in the rate of growth 

 of the injured and of the uninjured parts. 



"If the injury is slight, signs of an acceleration in the rate of growth will he 

 apparent in from 6 to 24 hours, and will continue for from 1 to several days. If the 

 injury is severe, the acceleration will be preceded by a period of retardation of 

 longer or shorter duration, depending upon the severity of the injury and upon the 

 condition of the plant injured. 



"The growth of the stems of older plants is accelerated by removal of a number 

 of the roots or leaves, but is not affected by a slight injury to the roots. 



"The roots of older plants as well as of seedlings are more independent than are 

 the stems or shoots. 



"The change in the rate of growth of higher plants under the influence of a 

 single irritation begins gradually, readies its maximum in from 12 to 96 hours, and 

 gradually diminishes until the normal rate is resumed. 



"A dilute but continuous atmosphere of ether, or a strong shock of ether of short 

 duration, will produce an acceleration in growth. 



"The total variation in the growth of higher plants due to the influence of a 

 single irritation is from to 70 per cent of the normal growth for the same period. 



"The growth of sporangium stalks of Phycomyces is suddenly and strongly 

 retarded by cutting either the mycelia or another sporangium stalk on the same 

 plant. The growth does not entirely cease, and gradually recovers its normal rate 

 in from 30 to 60 minutes. 



"•The influence of an irritation due to cutting or other injury is capable of acting 

 through a distance of several hundred millimeters." 



Periodicity of root pressure, M. 1>. Thomas (Proc. Indiana Acad. 

 8ci. } 1896, pp. 143-147). — The author gives in this paper, which is an 

 abstract of a more detailed presentation of the subject, the following 

 general conclusions: 



"The periodicity of root pressure seems to be inherent in the plant, and has either 

 been acquired by previous adaptation to environments, or as the results of the 

 action of some constant or periodic changes in the plant. As with the periodicity 

 of growth and other periodic phenomena, it does not always follow that periodic 

 change has not been produced by some constantly or continuously acting agent. 



"Root pressure does not seem to have any relation to the previous periodicities of 

 the vital activities of the plant when the top was connected with the roots. The 

 measure of the root pressure seems to be the osmotic activity of the root hairs, and 



