392 SCIENTIFIC RECOED FOR 1884. 



skies and full sunshine means high middaj- temperature and low tem- 

 peratures or frosts at night time ; high temperatures in the summer and 

 low temi)eratures in the winter. These extreme variations in tempera, 

 ture decide whether any given plant can thrive or not. The actual de- 

 velopment of the plant depends upon the action of sunlight. {Nature, 

 XXX, p. 392.) 



424. W. O. Atwater offers experiments to show that certain plants 

 grown under natural conditions do directly assimilate the atmospheric 

 nitrogen. 



425. [Although the amount of this assimilation is not at present suffi- 

 cient to be of any importance to meteorology, yet the establishment of 

 this fact, which has been controverted by so many eminent chemists, 

 wonld be of importance in studying the climates of past geological 

 epochs, when other plants and other gases were present.] {Nature, xxx. 

 p. 553.) 



426. C. Ferrari has published in the Agricultural Anuals^for 1883 a 

 comparison for Italy between the statistics of harvests and the meteor- 

 ological phenomena. He deduces a number of practical rules, such as 

 the more rain we have in summer the greater the harvest of corn ; but 

 for wheat, rye, and other grains great rain frequency is injurious, and 

 the harvest is greater as the temperature is higher and the cloudiness 

 less. 



427. Prof. H. EEoffmauu, communicating the result of the most recent 

 observations on the thermal constant of vegetation, compares the fig- 

 ures for a number of plants for Upsala and Giessen, and concludes that 

 the results agree quite as closely as can be expected, showing that there 

 is no change in the constant depending on latitude or climate. {D. M. 

 Z., I, p. 407.) 



428. General Strachey has endeavored to establish a simple method 

 of computing the quantity of heat received at any x)lace and ])roper to 

 use as a standard for comparison with the progress of vegetation. Eec- 

 ognizing the fact that it is not the absolute temperature that should be 

 summed up from day to day for tliis purpose, but that it is the excess 

 above a definite minimum and that below this minimum active vegeta- 

 tive processes are not possible. General Strachey has endeavored to es- 

 tablish the minimum limit and to devise convenient methods for sum- 

 ming up the excess above it. Numerical tables are given to assist the 

 computation. By assuming 42° F. a base temperature, it results that 

 a very close approximation is given by simply subtracting, this figure 

 from the true mean temperature on each pentade and summing the re- 

 mainders. {Z. 0. G. M., XIX, p. 425.) 



429. flu studies looking to the prediction of hatching of "locust" 

 eggs (see Reports of the United States Entomological Commission) the 

 present writer used 50° F. as a minimum limit for the development of 

 the eggs.] 



430. Dr. A. Frankel gives an account of experiments on the influence 



