RECENT ADVANCES IN SCIENCE 577 



of the seed-coats with hot water increased the permeability, 

 but the permeability of grape fruit and squash seed-coats was 

 not affected. In all cases except that of grape fruit extraction 

 with solvents of lipoid substances increased permeability, and 

 treatment with calcium chloride brought about a similar result. 



(b) Living Tissue. — Delf (Ann. of Bot. 30, 383-410, 191 6) 

 has made a study of the effect of temperature on the rate at 

 which water passes out of onion leaves and dandelion scapes 

 when these are under the influence of solutions slightly stronger 

 than isotonic (so-called subtonic solutions). The rate of water 

 loss was measured by the decrease in length of the tissue. The 

 method of measurement was very delicate, depending on the 

 use of an optical lever, and the changes in length of the tissue 

 could be continuously observed. Curves between shrinkage 

 and time were obtained with 0*18 and 0*3 molecular solutions 

 of cane sugar at a series of temperatures between 5° C. and 

 42 ° C. These curves are practically logarithmic, and the rates 

 of shrinkage at different temperatures are proportional to the 

 tangents of the angle made with the time axis by the tangents 

 drawn to the different time-shrinkage curves at points of 

 equal shrinkage. Temperature coefficients (Q10) of rates of 

 shrinkage and consequently of rates of water loss were found in 

 this way. They exhibited a good deal of variation, e.g. onion 

 1*4 between 5° C. and 15 C. and 3*0 between 30 C. and 40 C. ; 

 dandelion, 2*3 between io° and 20 C, and 3*8 between 20 C. 

 and 30 C. 



Observations on the influence of temperature on the intake 

 of water by potato tuber and carrot root have been made by 

 Stiles and Jorgensen (Ann. of Bot. 31, 415-34, 191 7). The 

 amount of water absorbed was measured from time to time 

 by the increase in weight of a number of thin uniform discs of 

 the tissue immersed in water. Curves were plotted between 

 time and increase in weight (swelling) for a number of different 

 temperatures, and temperature coefficients of swelling calcu- 

 lated in the same way as those of shrinkage were calculated by 

 Delf. Here again considerable variation in the temperature 

 coefficients was exhibited, e.g. Qi for potato between io° C. 

 and 20 C. was found to be 3*0, while that for carrot for the 

 same interval was only 1*3. 



Having regard to the complexity of the system under in- 

 vestigation, the variations exhibited in the results of both Delf 



