CHANGES ACCOMPANYING BREAKING OF REST PERIOD 15 



show that the respiration of the dried twigs noticeably decreased 

 day by day, while the respiratory activity of the frozen material was 

 not nearly so marked on the third day as it was on the first two days. 

 In this connection it should be mentioned that all buds on the 

 twigs which were given the preliminary treatment and then placed 

 in beakers of water in the greenhouse, burst within a few weeks. 

 The frozen twigs were a little ahead of the dried ones in beginning 

 growth and both were about one week ahead of those that were 

 untreated. 



EXPERIMENT 2. CO 2 PRODUCED BY ETHERIZED AND BY 

 UNTREATED TWIGS OF DIFFERENT SPECIES 



The species used in these experiments were Pyrus malus, Linn., 

 Fraximus Ornus, Linn., Quercus coccinea, Muench, and Morus alba, 

 Linn. One-year-old wood from young vigorous trees was used in 

 all cases. The twigs were collected and arranged in lots as pre- 

 viously described. Preliminary treatment was carried out in the 

 following manner: The six lots were placed in two 14-liter specimen 

 jars, as shown in Fig. 4, three lots in each jar. The jars were pro- 

 vided with screw clamp lids and rubber washers by means of which 

 they could be made air-tight. Just before fastening the lid of one 

 of the jars, ether at the rate of 0.5 cc. per liter of space, was poured 

 in. The lid was then screwed on immediately. The other jar was 

 closed up without adding any ether. The vessels were kept side 

 by side for twenty-four hours at a temperature of 20 C. 



Since neither jar contained water, no allowance had to be made 

 for absorption of ether by water. 1 The absence of water gave the 

 cut ends of the twigs a chance to become dry and plugged up. This 

 no doubt tended to minimize, tho not to entirely do away with, the 

 effect of injury on respiration. However, since the same number of 

 twigs were contained in each lot, error from this source would be the 

 same in all cases and hence its influence would not affect the com- 

 parative value of the results. 



The moisture lost during this preliminary treatment was prac- 

 tically the same in both etherized and unetherized material, the 

 amount lost never exceeding 0.5 of 1 per cent. (See Table 3). The 

 moisture lost was from transpiration. 



As soon as the preliminary treatment was over, the twigs were 

 placed in the respiration chamber and CO 2 determinations began. 



1. Johannsen, W. Das Aetherverfahren beim Friihtreiben, etc. Zweite 

 Anfl. Jena 1906. 



