500 
J. G. GROSSENBACHER 
tissues of substances having relatively high cryohydric points gave 
very little added resistance even though their molecular concentrations 
were high, while the introduction of substances with very low cryo- 
hydric points afforded much added resistance, even at fairly low con- 
centrations. He concluded that since the low-temperature death-point 
can be lowered by the introduction of substances of low cryohydric 
points, protoplasm can have no specific death-point, but that the 
death-point depends upon the temperature at which water and other 
substances are crystallized out. Some interesting experiments by 
Gassner and Grimme^^ also show that Maximow's results have a wide 
application. 
The part played by enzymes in plants injured by low temperatures 
is still rather uncertain, though they are probably involved in the 
many protoplasmic changes that result. It seems very likely, too, 
that some of the harmful changes that are caused by low temperatures 
are due to the perverted action of enzymes no longer properly con- 
trolled by substances that have been modified by the cold. Kras- 
nosselsky^® found that an oxidizing enzyme evinced more activity in 
sap expressed from a frozen plant than in that obtained from living 
tissues. The browning of sap expressed from tissues injured by cold 
is suggestive of the brown-spotting of herbaceous plants obtained by 
Molisch in experiments cited above, in which low temperatures above 
the freezing point were used. Mobius" obtained very similar results. 
At any rate, it has been well established that the best known enzymes 
present in plants are not destroyed by ordinary low temperatures, 
for Palladin^^ and his students use low temperatures to kill tissues 
before extracting enzymes. Kovchoff^^ maintains that protein-split- 
ting enzymes are very active in cold-injured plant tissues, though his 
experiments seem to admit the assumption that perhaps the proteins 
were split as a direct result of the low temperature and that the 
25 Gassner, G., und Grimme, C,, Beitrage zur Frage der Frostharte der Getreide- 
pflanzen, Bericht. Deutsch. Bot. Ges. 31: 507. 1913. 
2^ Krasnosselsky, T., Bildung der Atmungsenzyme in verletzten Pflanzen, 
Bericht. Deutsch. Bot. Ges. 23: 142. 1905. 
2^ Mobius, M., Die Erkaltung der Pflanzen, Bericht. Deutsch. Bot. Ges. 25: 
67. 1907. 
28 Palladin, W., tJber den verschiedenen Ursprung der wahrend der Atmung der 
Pflanzen ausgeschiedene Kohlensaure, Bericht. Deutsch. Bot. Ges. 23: 240. 1905. 
29 Kovchoff, J., Enzymatische Eiweisszersetzung in erfrorenen Pflanzen, 
Bericht. Deutsch. Bot. Ges. 25: 473. 1907. 
