Killing of Plant Tissue by Low Temperature 219 



young outer ends of potato shoots to withstand lower temperatures 

 than would the older basal portion. Rein^ found young onion leaves 

 more hardy than older ones. Winkler- found young one-year-old 

 needles of evergreens more hardy than older ones. Shumacher^ 

 found young yeast cells more hardy than older ones. Fisher^ found 

 newly formed colloids to regain their normal characteristics after 

 being exposed to a low temperature that would irreversibly change 

 older colloids. On the other hand Bartetzko found that young 

 cultures of Aspergillus niger would not withstand as low temperatures 

 as would older ones. It seemed worth while to make some freezings 

 to determine whether or not plant tissues making rapid growth are 

 generally frozen to death at higher temperatures than are tissues 

 growing more slowly. Leaves of various plants were used, leaves 

 that were certainly full grown in case of those from fruit trees and 

 leaves that had apparently ceased growing, in case of plants like 

 lettuce, cabbage, kale, etc., were frozen at the same time with young 

 rapidly growing leaves from near the growing tips of the stem. The 

 following table gives the results: 



iZcits. f. Naturw. Vol. 80 (1908) p. 1. (Blbl. No. 92). 



2Jahrb. f. Wiss. Bot. Vol. 52, 1913, pp. 467-506. (Bibl. No. 121). 



'Sitzungsber der Math. Phys. Klasse d. Wiener Akad. d. Wiss. Alt. 1, 1874. (Bibl. No. 

 103). 



<Beitr. Biol, der PH. Vol. 10, pp. 133-234, 1911. (Bibl. No. 40). 

 sjahrb. f. Wiss. Bot. Vol. 47, pp. 57-98 (1911). (Bibl. No. 8). 



