394 BOTANICAL GAZETTE [JUNE 
freezing point of the tissue is reached. This, in the case of buds; 
lies at about —3.5° C. to —2.3°C. Hence, if tissues which have been 
subjected to—18° temperature in the open are to be observed with 
the maximum ice content, it must be while the temperature is still 
low. If in the morning the temperature has risen to —7° C. before 
observations are made, very little more ice will be found than if the 
cooling to —7° C. had just taken place.'3 
6.—Syringa vulgaris: same section as in fig. 3 thawed in the laboratory; 
note sponging out of tissue and closing of spaces occupied by the ice. 
13 GOEPPERT gives a similar experiment. “Twigs with buds of Cornus mas- 
cula, Prunus Cerasus, and Aesculus Hippocastanum were on January 2, 1871, placed 
ten hours at a temperature of —16 to —20° C. Then while frozen stiff they were 
eri into the warm tube of an oven at 25° C. and placed in water for further obser- 
tion. They waht a later just as others that had not been subjected to this 
riment.” Some other experiments with herbaceous plants led GOEPPERT to 
iain that in most cases alternate thawing and freezing, when taking place many 
times, gradually weakened the tissue. Ueber das tseFeleie Erfrieren der Pflan- 
zen und Schutzmittel dagegen. Stuttgart, 1883, pe 33. 
Warttrn believes that rapid thawing gat freezing is very detrimental to the 
a eT 
