CHANGES ACCOMPANYING BREAKING OF REST PERIOD 11 



Object of the Experiments. During these studies, conducted 

 in 1913-14, respiration experiments were carried out with the follow- 

 ing objects in view: 



1. To determine the effect of previous drying and of previous 

 freezing on the CO2 production of dormant apple twigs. 



2. To determine the influence of the same dose of ether on the 

 CC>2 production of dormant twigs of different species. 



3. To determine the effect of the same dose of ether on the CO 2 

 production of dormant apple twigs at different times during the 

 season. 



Method of Collecting Material. The importance of obtaining 

 representative material and uniform lots for comparative experi- 

 ments, was carefully considered. The plan of securing twigs for the 

 experiments was as follows: In all cases, one-year-old twigs, i. e., the 

 growth which had been made during 1913, were used. This material 

 had been exposed to the environment the shortest time, and hence 

 had not as much chance to become altered in one way or another as 

 older material. The twigs used were fully matured, each specimen 

 having formed a normal terminal bud. They were taken from the 

 tops of the trees where all had had the same exposure to sunlight and 

 other conditions. Only those twigs which had made from 20 to 30 

 cm. growth were collected. They were cut from the tree just above 

 the last annual ring. Where twigs were obtained from more than 

 one tree, the material from each tree was kept separate until divided 

 into lots. When a series of comparative experiments was to be made, 

 the material was secured from the same trees, and just as much was 

 taken from every tree as was used from that particular tree in the 

 other tests. For example, if material was secured from trees Nos. 

 1, 2, 3, etc., each tree yielding fifty twigs, when the same experiment 

 was to be repeated a few weeks later, fifty twigs would be collected 

 from each of trees Nos. 1, 2. 3, etc. 



After the material was secured, the samples from each were 

 divided into similar lots in the following manner: All the cut sur- 

 faces of the twigs were placed down, the terminal buds up. The 

 bunch of twigs was held loosely between the hands, and then jolted 

 up and down on the table until all cut ends stood on the same level. 

 Then the lot was held with one hand, and with the other, the twigs 

 were distributed one at a time commencing with the longest and 

 ending with the shortest. If the material from each tree was divided 

 among six lots, Nos. 1, 2, 3, 4, 5 and 6, then No. 1 would receive the 

 first twig, and No. 6, the sixth; the seventh twig would go to No. 6 

 and the twelfth and thirteenth to No. 1, etc. When the material 



