TUKGIDITY 75 



nomenon in the case of turgid root hairs, from which droplets 

 of solution are exuded. It is probable that in these cases 

 we have to do with a phenomenon related to glandular 

 secretion. 



Another potent cause for great increase in protoplasmic 

 permeability in some instances is lowering of temperature. 

 If a filament of any common alga be carefully dried exter- 

 nally and placed in olive oil whose temperature is then 

 rapidly lowered to the vicinity of C., a film of water may 

 be seen to form about the filament, and partial plasmolysis 

 may be observed. When the temperature is again brought 

 back to normal, the extruded water is again absorbed. 

 Greeley * has recently shown, not only that complete plas- 

 molysis can be produced in Spirogyra by low temperature, 

 but that the same thing occurs in Stentor coeruleus. Exactly 

 the same phenomenon is exhibited by Stentor individuals 

 when water is removed from them by the action of a con- 

 centrated sugar solution. The animals plasmolyzed by low 

 temperature return to their normal activity with rise in tem- 

 perature, but Greeley was unable to cause the same reversal 

 in the case of the osmotically plasmolyzed individuals. I 

 have often observed that the liquid exuded from cells of 

 Spirogyra plasmolyzed by cold is a solution. Its freezing 

 point is considerably lower than that of pure water. 



The theory of death by freezing which was advanced by 

 Molisch 2 accounts for the decline of activity and for final 

 death at low temperatures by the extraction of water from 

 the protoplasm until the processes which make up life are 

 no longer possible. Matruchot and Molliard 3 have pointed 



i A. W. GKEELEY, " On the Analogy between the Effects of Loss of Water and 

 Lowering of Temperature," Am. Jour. Physiol., Vol. VI (1901), pp. 112-28. 



2H. MOLISCH, Untersuchungen Uber das Erfrierender Pflanzen, Jena, 1897; 

 reviewed in Bot. Centralbl, Vol. LXXIII (1898), p. 149. 



3L. MATROCHOT AND M. MOLLIAKD, "Sur I'identit6 des modifications de 

 structure produites dans les cellules v6g6tales par le gel, la plasmolyse, et la 

 fanaison," Compt. rend., Vol. CXXXII (1901), pp. 495-8. 



