50 PHYSIOLOGY [BoT. Absts., Vol. X, 



isolated. The author believes that this relation of dominance and subordination is not a 

 matter of chemical or transportative correlation but is due to the transmission of an excita- 

 tion through the living protoplasm. It is possible to produce such gradients by exposing 

 undifferentiated cells to localized external stimuli. He discusses the electro-chemical con- 

 ception of the transmission of excitations proposed by R. S. Lillie. Among plants the author 

 has worked with Bryophyllum calycinuvi, Phaseolus multiflorus, and Saxifraga sarmentosa. 

 By cooling a zone of the petiole or stem he succeeded in preventing the dominance of the apical 

 region over parts below the cooled portion without interrupting the upward flow of liquids 

 through it. These experiments provide further evidence that in plants the correlative factor 

 is not a transported substance but a transmitted excitation. — E. W. Sinnott. 



TEMPERATURE RELATIONS 



.303. Appleman, Charles O., and S. V. Eaton. Evaluation of climatic temperature 

 efficiency for the ripening processes in sweet corn. Jour. Agric. Res. 20:795-805. 1921, — 

 An ear of sweet corn is considered ripe when the growth of kernels ceases and the chemical 

 changes in the corn have nearly attained equilibrium positions. The maturing of ears con- 

 sists essentially in the loss of water. The important change in percentage composition of 

 corn during ripening consists in the depletion of sugar and the increase of starch. In early 

 stages of ripening, reducing sugars predominate so that the highest total sugar content may 

 not represent the stage of greatest sweetness. On a dry weight basis, the changes in fat, 

 crude fiber, and total nitrogen occur in the very early stages of ripening, and subsequently 

 they remain fairly constant. Consequently, the rate at which the ratio of total sugar to starch 

 decreases is a good measure of the ripening date. Temperature is the controlling factor for 

 the rate of ripening. Several temperature indices were employed to evaluate climatic temper- 

 ature efficiency for the ripening process, but exponential indices were found to furnish the 

 best criteria. The rate of ripening in sweet corn, for a wide range of temperature, adheres 

 rather strictly to the van't Hoff-Arrhenius principle, and as this rate is inversely proportional 

 to the exponential indices a basis is furnished for prediction within 1 day of the number of 

 days required in different localities and at different seasons in the same locality for sweet 

 corn to pass from the beginning of kernel formation to the best edible stage, as well as the 

 number of days that the corn may be expected to remain in this condition. — D. Reddick. 



304. EsTY, J. R., AND P. H. Cathcart. The change in the hydrogen-ion concentration 

 of various mediums during heating in soft and pyrex glass tubes. Jour. Infect. Diseases 29: 

 29-39. 1921. — In thermal death point determinations, the hydrogen-ion concentration of the 

 solution must be known during the entire period of heating. The type of glass to be used for 

 this purpose is important, since heating the solution in the glass greatly affects the hydrogen- 

 ion concentration, particularly when soft glass tubes are used. In the case of juices from 

 canned corn, peas, string beans, spinach, beets, sweet potatoes, and pumpkin, the hydrogen- 

 ion concentration is less affected by soft glass tubes than by hard glass. — Selman A. Waksman. 



305. Fawcett, Howard S. The temperature relations of growth in certain parasitic fungi. 

 Univ. California Publ. Agric. Sci. 4: 183-232. Fig. 1-11. 1921.— This is a study of vegetative 

 growth of Phytophthora terrestria, Phomopsis Citri, Pythiacystis citrophthora, and Diplodia 

 natalensis at maintained temperatures. Careful consideration was given to: (a) The nature 

 of the organism (the previous history of the fungus), (b) the nature of the medium, (c) temper- 

 ature conditions, (d) radiation conditions, and (e) the duration condition. The observations 

 were based on the diameter increments of the mycelial disk as it grew over the surface of a 

 corn-meal agar plate. The diameter increments were considered as rates, expressed in milli- 

 meters per 24 hours. — In general form and shape the growth-temperature curves of the 4 fungi 

 studied were much alike in the second 24-hour period. Beginning with the lowest temperature 

 tested, the curves all rise gradually to maximum values, then descend rapidly to minima as 

 the highest temperatures permitting growth were approached. However, the growth- 

 temperature curves for each organism show characteristic differences in subsequent 24-hour 

 periods. The apparent temperature optimum and maximum were lower at each successive 



