New York Agricultueal Experiment Station. 291 



subject to winter- injury while that on those growing at a more mod- 

 erate rate may be practically immune. 



Further observations on apple trees experimentally injured by low 

 temperature. — The three remaining trees which had been treated 

 with a freezing mixture on September 14, 1911, in a seedUng orchard 

 at Geneva, were re-examined on June 3, 1912, and found to have 

 changed much in appearance. (See page 279.) Tree 1/25 had 

 sparse and undersized leaves which were of normal color. The tree 

 bore a few small fruits. Many of the distal portions of branches and 

 numerous small spurs had died back and had large numbers of 

 pycnidia of Cytospora broken through the periderm. The branches 

 and leaf area had apparently been reduced by a shortage in the water 

 supply. 



Circular " pit-cankers " of various sizes surrounded the numerous 

 " shot-holes " which were made by a bark beetle (Scolytus) a few 

 days after the trees had been subjected to low temperature. The 

 dead pits varied from about 4 to 14 mm. in diameter and most of 

 them had been delimited from the live tissues around them by 

 newly formed cork layers. However, quite a number of the largest 

 ones on the stem and main branches and many of those on the abaxile 

 side at the bases of twigs and spurs had failed to form new cork layers 

 between the dying bark and the wood, and thus resulted in the forma- 

 tion of small circular pits circumscribed by a fissure as shown in 

 figure 8 on Plate XXIX. 



The remaining bark on the basal part of the stem had died and the 

 wood underneath had become discolored nearly to the pith. The 

 other wood in the girdled region had a normal color to within about 

 5 mm. of its outer surface. A thin callus had formed along the upper 

 edge of the girdle. 



Tree 2/9 was nearly dead; practically none of the last year's buds 

 had leafed out although the branches had died back only about half 

 way to the main crotches. Numerous small adventitious shoots had 

 arisen on the living portions of the stem and main branches. The 

 leaves on these shoots had a normal color but they were much curled 

 and distorted by aphides. 



The pit cankers were more commonly of the larger type and ex- 

 tended to the wood, although there had been sufficient growth to 

 cause their delimitation from the surrounding bark by fissures. 



The remaining bark around the base of the trunk had died and 

 the wood underneath it was not only stained to the pith but partially 

 decayed and permeated by the mycelium of some fungus. The 

 other portions of wood had a normal color to within about a centi- 

 meter of the exposed outer surface. Practically no callus had devel- 

 oped along the upper limit of the dead girdle. Strips of bark from 

 1 to 5 cm. wide along both sides of the slits made before the tree was 

 frozen, were partially loose and dead, with numerous pycnidia of 



