430 EXPERIMENT STATION RECORD. 



In order that plants may flower a dormant period is necessary, as only then 

 are they susceptible to the factors which are concerned in the opening of the 

 flowers. In his experimental studies the author found that dormant twigs 

 placed for several hours in hot water (28 to 30° C.) had their buds forced, 

 while those not dormant were insensible to the treatment. Placing them in 

 hot air also stimulated shoots, but the stimulus did not continue so long as on 

 treatment with hot water. 



Phenological observations are held to furnish only approximate results 

 concerning the effect of climatic influences on plants. 



The influence of light on the transpiration of succulent plants, Leclerc 

 DU Sablon (Compt. Rend. Acad. Sci. [Paris], 153 (1911), No. 2J,, pp. 123G-1238).— 

 Experiments were conducted with a number of species of succulent plants to 

 determine the effect of diffused and direct sunlight on their respiration, the 

 claim having been made that sunlight increases the transpiration of chlorophyll- 

 bearing plants only, while diffused light tends to increase the transpiration not 

 only in green but also in etiolated plants. 



It was found that diffused light when compared with darkness exerted a 

 greater influence than did direct sunlight when contrasted with diffused light. 

 The stimulating effect of direct sunlight is held to be a result of the increased 

 temperature following the exposure of the plant to the full effect of sunshine. 



On the infl.uence of ultraviolet rays on vegetation, J. Stoklasa et al. 

 iCentbl. Bakt. [etc.], 2. AM., 31 {.1911), No. 16-22, pp. Jf77-.',95, pis. //).— Con- 

 tinuing previous contributions (E. S. R., 25, p. 125) the authoi's report further 

 researches with the shorter wave lengths as related to chlorophyll synthesis, 

 protoplasm destruction, and leaf development, with results as follows. 



Seedlings of pea, corn, oats, and rye gi'own in darkness for 10 days and then 

 exposed to waves of from 0.000250 to 0.000575 mm. in length showed a dis- 

 tinctly green color in 2 hours, while those exposed to direct sunlight remained 

 a pale yellow. After 6 hours' exposure, however, both showed a deep green of 

 about the same intensity, and thereafter the rates of change were about equal. 

 Seedlings grown in darkness for about 21 days appeared to have been so 

 weakened that these rays produced only slow and slight change in this experi- 

 ment. Etiolated leaves of the sugar beet were exposed for 134 hours to rays 

 of from 0.000250 to 0.000575 mm. length, others for 14 hours to diffused day- 

 light, while still others were kept in darkness as controls. On comparison it 

 was found that the leaves of the control plants were distinctly yellow and the 

 edges curled sharply back upon the lower side, the primary veins being promi- 

 nent while the secondary veins were scarcely noticeable. The leaves which 

 had been exposed to daylight were of a greenish yellow, the edges were a 

 little curled, the secondary as well as the primary veins being quite distinct. 

 The leaves exposed to the short wave lengths were of an intense green, com- 

 pletely unrolled, and sharply crisped at the edge, both primary and secondary 

 nerves being very distinct and prominent. These leaves were unusually stiff 

 and somewhat brittle, and when cut off and placed in water retained their 

 fi-esh a])pearance for a week, whereas those of the other 2 groups did not last 

 half so long. 



INIost of the wave lengths used in the above experiments were between 

 0.000300 and 0.000400 mm., but experiments were conducted also with the 

 mercury-quartz lamp without the protective globe, giving additional wave 

 lengths shorter than 0.000300 mm. These showed practically the same results 

 in chlorophyll formation as previous ones, and apparently these shorter waves 

 have no influence in this regard. No destruction of chlorophyll was noted 

 after 2 hours' exposure. Young green leaves of different plants exposed to 

 these direct rays for 2 hours showed a deep green color. In 4 hours they 



