12 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN NO. 21 



from the second tree was distributed, No. 6 received the first and 

 No. 1 the sixth and seventh, etc. The material from each tree was 

 distributed in a similar manner. In the end, these composite samples 

 were almost exactly alike. Each contained the same number of 

 twigs; each had just as many twigs from any single tree as the other; 

 and every lot had just as many long and just as many short twigs as 

 the others. The efficiency of this method of distribution was shown 

 by the fact that the weights of the composite samples obtained in 

 this way never varied more than 2 or 3 per cent. Incidentally, it 

 was considered necessary to have the same number of twigs in each 

 lot, because each twig had received a wound and wounding affects 

 respiration. Altho other precautions were taken to offset the effects 

 of this wounding, still if the precautions were not entirely adequate, 

 then the effect on respiration by the injury would be the same in all 

 lots, and the results would still be comparative. 



Apparatus. The general appearance of the apparatus used for the 

 determination of the CO 2 production of the twigs, is shown in Fig. 1. 

 The respiration chambers proper consisted of six slender specimen 

 jars. Each chamber with its accompanying parts formed a single 

 unit. The diagram shown in Fig. 2 illustrates in detail the construc- 

 tion of one of these units. The chamber "5" had a capacity of 

 2.5 liters. Before the air entered this chamber, it was freed from 

 CO 2 by passing tho the saturated solution of KOH in tube ''6." 

 It left the chamber, together with the CO 2 produced by the twigs, 

 thru the glass tube "13" which opened at the bottom of the jar. 

 The moisture was taken up by the CaCl 2 in tube "14." The CO 2 

 produced by the twigs was absorbed by the saturated solution of 

 KOH in the Geissler bulbs "7". A CaCl 2 tube "8" retained all 

 moisture which evaporated from the bulbs. 



In setting up the apparatus, the weighed twigs were placed in 

 chamber "5" after which the two-hole cork was inserted. Then 

 the glass tubes for the incoming and for the outgoing air were passed 

 thru the cork. The KOH and the CaCl 2 tubes were connected to 

 the respective glass tubes. After this a strip of heavy paper (2) 6 

 cm. wide, was tightly wrapped around the glass flange at the top of 

 the jar. This paper form was held firmly by means of a rubber 

 band. Melted paraffin was then poured over the cork to a depth of 

 from 1 to 2 cm. This sealed all possible openings thru which there 

 might be leakage of air. 



The absorption bulbs were connected by means of rubber 

 tubing. They were weighed on a delicate balance. 



