314 PHYSIOLOGY [BoT. Absts., Vol. VII, 



that the condition of the roots is of the greatest importance in determining whether a plant 

 recovers or not, i.e., whether the roots are in condition to supply the water to replace that 

 removed from the tisssues by the low temperatures. — F. M. Blodgett. 



2156. Peters, R. A. Nutrition of the protozoa. The growth of Paramoecium in sterile 

 culture medium. Jour. Physiol. [London] 53^: cviii-cix. 1920. — A medium for the success- 

 ful cultivation of a pure culture of Paramoeciuin contained the following: NaCl, KCl, CaCl2, 

 Na2HP04, KH2PO4, MgS04, NaHCOs, phenol red, glucose, histidine, arginine, leucine, ammo- 

 nium lactate, and traces of FeCU, KI, and MnS04. When single amino acids are supplied, 

 histidine, arginine, or leucine gives a much more rapid growth than tryptophane. Galac- 

 tose and fructose, but not maltose, may be substituted for glucose. — Ernest Shaw Reynolds. 



GROWTH, DEVELOPMENT, REPRODUCTION 



2157. Friesner, Ray C. Daily rhythms of elongation and cell division in certain roots. 

 Amer. Jour. Bot. 7: 380-407. 2 pi. 1920. — Previous work on rhythm of elongation and cell 

 division in plants is summarized. Hourly observations were made on the elongation of root 

 tips of several species which were grown in a dark room and kept under constant temperature. 

 Material from roots growing under these conditipns was killed every 2 or 3 hours and studied 

 microscopically to determine rate of cell division. Elongation in all cases was found to pro- 

 ceed in a rhythmical manner, 2 or more waves occurring during a 24-hour period. The time of 

 occurrence of maxima and minima is dependent upon the time of initiation of metabolic 

 activity rather than upon time of day by the clock. Cell division proceeded in a similar 

 rhythmic fashion. The maxima and minima for elongation as compared to cell division 

 were generally found to alternate with one another, only rarely occurring simultaneously. The 

 author suggests that this alternation is perhaps due to the lack of sufficient energy to permit 

 both processes to go on at the same time at their maximum rates. He believes that this 

 reciprocal relation between elongation and cell division accounts for most of the rhythms 

 found in these plants. — E. W. Sinnott. 



2158. MuRRiLL, Wm. a. The dendrograph — an instrument that keeps tabs on tree growth. 

 Sci. Amer. 122 : 595. 3 fig. 1920. 



2159. Pfeiffer, T., und W. Simmermacher. Uber den Einfluss der Steine im Boden 

 auf das Wachstum der Pfianzen. [The influence of stones in the soil upon the growth of 

 plants.] Landw. Versuchssta. 93: 49-63, 277-284. 1919. — Two series of experiments to deter- 

 mine the effect of stones in the soil upon the growth of plants are reported. In the first 

 series oats was used as the test crop, and in the second carrots. The experiments were con- 

 ducted in earthenware pots, equal weights (3.4 kgm.) of a loam soil being used in all cases. 

 Gravel stones from 1 to 3 cm. in diameter were mixed with the soil in 3 series of pots in 3 dif- 

 ferent proportions, namely 25, 50, and 75 per cent. The cultures were compared with a con- 

 trol series containing only the 3.4 kgm. of soil. All pots were regularly watered to satura- 

 tion with uniform nutrient solutions. — The results show practically the same top and root 

 development in all cases with both oats and carrots, and lead to the conclusion that with 

 equal amounts of water and nutrients, the presence of stones in the soil had no influence upon 

 plant production. — A. T. Wiancko. 



2160. Reed, H. S. Slow and rapid growth. Amer. Jour. Bot. 7: 327-332. 2 fig. 1920.— 

 The growth in length of shoots from pruned and unpruned apricot trees was measured weekly 

 during the growing season. A close correspondence was found between the growth rates 

 in these two cases and the differential equation for growth rate previously proposed by the 

 author [x = a{l — e~^^), where x is the size of the organism at time t, a the final size attained, 

 and k a constant.] The rate of growth of these shoots, which is much higher in pruned than 

 in unpruned trees, thus seems to depend upon the final length which they attain. The author 

 suggests that growth is some sort of a catalytic process, the organism being the end product 

 of a process in which a catalyst acts upon a substrate. — E. W. Sinnott. 



