286 Report of the Botanical Department of the 



2 dm. where the bending had occurred. The general appearance was 

 that of so-called " sun-scald." The affected bark was rusty brown in 

 color and the phloem region was much disorganized. 



Effect of low temperature on the diameter of apples and potatoes. — 

 On January 8 some medium-sized potato tubers and apples were 

 carefully measured with a caliper by adjusting it against the heads 

 of two pins which had been stuck into the specimens at opposite 

 points of the greatest diameter, up to the heads. Afterwards they 

 were placed out of doors and left there over night with the tempera- 

 ture ranging around — 27° C. Early the next morning one was taken 

 in at a time and remeasured over the pin-heads. The data are re- 

 corded in the following table: 



Table III. — Changes in Diameter of Apple Fruit and Potato Tubers Induced 



BY Low Temperature 



Apple No. 1, diameter in evening 77.5 mm., in morning 77.4 mm. 



This shows an average decrease in the greatest diameter of the 

 apples of 0.16 mm. or about 0.2 per ct.; and an average increase in 

 the longest diameter of the potato tubers of 1.75 mm. or about 

 1.7 per ct. 



Discoloration, after thawing, of structures injured hy low temperatures. — 

 Winter- or low-temperature injured plant structures can usually not 

 be recognized as being injuriously affected until after they have 

 thawed and become discolored. However, in some instances injuries 

 may be seen by microscopic examination immediately after thawing 

 or even v/hile frozen. Some of the potatoes and apples used in the 

 above experiment were placed outside an east window and the others 

 were thawed and cut in pieces for microscopic examination and for 

 observing the development of discoloration in air, water, etc. 



The thawed tubers were very soft but of normal color. The 

 " sap " could be squeezed out with the hand as readily as water from 

 a sponge. By using thin hand sections it was easily seen that many 

 of the cells had been broken and others separated along the middle 

 lamellae. The thawed apples were soft also but not spongy like the 

 tubers. Fewer cells were broken and separated, in fact at the calyx 

 end there was practically no indication of injury. 



Pieces of tubers were placed into 15, 30, 50, 70, 80, 95 per ct., and 

 absolute alcohol; in distilled water, and into 2 per ct. formalin. 

 Pieces of both apple and potato were exposed to the air over night. 



On the follo^vdng day the pieces of potato exposed to air had become 



