226 EXPERIMENT STATION RECORD. [Vol.36 



march of transpiration during tlie growth period and the extent to which the 

 daily transpiration is correlated with various weather factors. 



During a 10-day period of maximum transpiration the daily loss of water 

 from small grains ranged from 12 to 16 times the dry weight of the crop har- 

 vested ; from millets, corn, and sorghums, 6 to 9 times; and from alfalfa, 36 

 to 56 times. The loss of water from the small grains during the period of maxi- 

 mum transpiration amounted to 1.5 kg. per square meter of plant surface per 

 day ; from Sudan grass, 0.8 kg. ; and from alfalfa, 1.6 per kg. These amounts 

 are said to be from 5 to 14 per cent of the loss during the same period from a 

 free water surface of equal area. 



In considering the march of transpiration due to changes in the plant alone, 

 transpiration in annual crop plants is found to rise to a maximum a little be- 

 yond the middle of the growth period, after which it decreases until the plants 

 are harvested. With perennial forage crops, such as alfalfa, there is a steady 

 increase of transpiration to a maximum at or near the time of cutting. 



Correlation coefficients are shown for the different physical factors of environ- 

 ment as related to the transpiration of different crops. Small grains show indi- 

 vidually a markedly higher correlation between transpiration and the intensity 

 of the various physical factors than was observed when all the crops were 

 combined in one population. Corn, sorghums, millets, and legumes show a some- 

 what lower correlation between transpiration and the intensity of the physical 

 factors of ejivironment. The plants of all crops show, however, the same rela- 

 tive dependence of transpiration on physical factors. 



Self-warming in flowers of night-blooming Cereus, E. Leick (Ber. Deut, 

 Bot. GeselL, 3^ {1916), No. 1, pp. 14-22). — Reporting results of experiments 

 carried out in 1902 and 1904 in the botanical institute at Greifswald with C. 

 grandiflorus and C. pteranthus, the author states that the flowers show a 

 certain amount of self-warming, but that this does not in every case make 

 good the loss due to transpiration and is too small to be of much biological sig- 

 nificance. The excess temperature is related to the size of the flower and is 

 greater when it is closed and when the humidity is high, but it shows no real 

 periodicity and disappears at the close of the blooming period. Anthers gen- 

 erally develop more heat than the other floral parts. 



Measurement of evaporation rates for short time intervals, E. S. Johnston 

 and B. E. Livingston {Plant World, 19 {1916), No. 5, pp. 136-140, fig. 1).— 

 Noting the limitations of atmometers previously discussed (E. S. R., 34, p. 34), 

 the authors describe herein a form of spherical porous cup atmometers in 

 which the intensity of evaporation, which varies from time to time, may be 

 made to indicate its value at any given time by the height of a column of mer- 

 cury affected by the fluctuations in pressure. 



A field auxanometer, G. N. Collins and J. H. Kempton {Jour. Wasli. Acad. 

 Sci., 6 {1916), No. 8, pp. 204-209, figs. 3).— It is believed that the principal re- 

 quirements for securing satisfactory measurements of the growth of plants in 

 the open have been met by a contrivance which is described. The cost is said 

 to be sufficiently low to permit a number of plants to be studied at the same 

 time. The essential features are a pasteboard mailing tube, around which is 

 secured the record sheet, mounted on an axis attached to the winding stem of an 

 ordinary alarm clock lying on its face, and a marker adjustably attached to a 

 glass rod suspended from a pulley and counterbalanced, its lower end being 

 fastened to the top of the growing plant. The whole contrivance is inclosed 

 in a box with glass front and attached adjustably to a vertical post driven 

 near the plant to be studied. The advantages of the machine are described. 



