732 EXPERIMENT STATION EECORD. 



intercepted in its course by the first roots basal to the leaf from where it starts, 

 and does not go beyond it. 



The bearing of the results of these experiments on the cultivation of the sweet 

 potato is quite evident, as they show that any portion of a mauy-rootetl sweet 

 potato plant may draw water from the roots most favorably situated, which 

 are those in the main hill, so that whone^•er a drought occurs the rooted 

 branches will draw water from the main hill. Evei-y rooted Joint of any 

 branch intercepts all the starch brought from all the leaves beyond it and 

 allows none to pass to the main hill. In a dry time a rooted branch may feed 

 upon the main root, but in the best growing time it does not help the crop of 

 the main plant in the least. 



The stomatograph, W. L. Balls {Xature [London], 87 (1911), No. 2180, p. 

 180; Proc. Roy. Hoc. [London], Ser. B, 85 {1912), No. B 576, pp. 33-4h figs. 

 5). — The appliance here described and discussed is said to be a self-recording 

 modification of Darwin's poronieter (E. S. R., 27, p. 222), indicating changes 

 in stomatal aperture by recording variations in the quantity of air forced 

 through a leaf. It is claimed to be extremely easy to use, independent of 

 weather changes, and especially adapted to outdoor conditions such as are 

 met with in agricultural and ecological studies. Records obtained with 

 Egyptian cotton indicated that this instrument may be of great utility in 

 the study of purely economic matters connected with irrigation, and it is 

 thought also that it may replace aspirators for many kinds of scientific re- 

 search. The results of some studies on the behavior of stomata are given, 

 and the significance of these stomatal changes as related to carbon dioxid 

 assimilation in the growth of the plant is also discussed. 



Photosynthesis and stomatal aperture, W. L. Balls {Nature [London], 89 

 {1912), No. 2231, p. 555). — In the i)aper noted above the author, having found 

 that Egyptian field cotton plants showed stomatal opening practically only 

 from 6 a. m. to 12 m., reaching a maximum about 9 a. m., expressed the ex- 

 pectation that (1) this afternoon closure might be found to provide a lim- 

 iting factor on i)hotosynthesis by restricting the inward diffusion of carbon 

 dioxid; and (2) since the theoretical possibilities of carbon dioxid assimi- 

 lation have probably never yet been approached and since the stomata are 

 wide open for an hour or two in the morning, record values in carbon dioxid 

 assimilation might be obtained at the times of such maximum aperture. 



The present brief report states that both these expectations have been 

 fulfilletl. It was found that assimilation was very greatly reduced, if not 

 inhibitetl entirely, during the afternoon by the closing of the stomata. Some 

 other data obtained are reported in this connection. 



Reversible changes in permeability produced by electrolytes, W. J. V. 

 OsTERHOUT {Science, n. so:, 3(j {1912). No. 92.'i, pp. 3.50^.52).— Different 

 opinions being held regarding the property of permeability of the cell, the 

 author has investigated it to determine whether there are reversible changes 

 which involve no injury and which may form a normal part of the activity 

 of the cell. If such changes occur it is believed that they may control the 

 course of metabolism. 



Disks were cut from living tissue of the fronds of common kelp and their 

 electrical conductivity in various solutions determined. It appeared that 

 the permeability may be greatly decreased and then restored to the normal 

 sevei'al times on five successive days without any trace of injury. Experi- 

 ments with dead tissues, killed by heat or formalin, showed that the results 

 were due entirely to the living cells. 



It is concluded that it is possible to cause I'apid and large changes in 

 permeability by means of electrolytes, that these changes may consist in 



