240 MINNESOTA BOTANICAL STUDIES. 



level with the surface of the ground outside. On this table 

 was placed the registering balance connected with a Frost 

 time recorder.^ 



The laboratory received the sunlight from 8 a. m. to 5 p. m. 

 and was ventilated in such a manner that the conditions of 

 moisture and humidity were practically the same as those of 

 the outside air. Access to this room was allowed only to per- 

 sons immediately concerned in the experiments, to avoid dis- 

 turbance of balances. 



A recently formed fruit at a distance of 60 cm. from the 

 tip of the vine was placed on the scale pan on the extended 

 upright from one arm of the beam outside of the case of the 

 balance.* 



The scale plan was covered with cotton wool to afford a 

 suitable resting place for the fruit. In this position the fruit 

 was a few centimeters distant and directly in front of a large 

 window with southern exposure. At a distance of 25 cm. 

 from the scale pan toward the root the vine was firmly fastened, 

 on a level with the fruit, to an upright support. In this position 

 the flexibility of the stem was very great and was moreover 

 quite constant. The scale pans were allowed to swing through 

 a vertical arc of nearlj^ 2 cm. and very delicate registrations 

 could be secured. The terminal portion of the vine as well as 

 two or three side shoots was cut away at a distance of 12 cm. 

 beyond the fruit. The cut surfaces were sealed to prevent 

 undue exudation of water. Attached to the vine near the point 

 of support were two leaves whose weight did not fall upon the 

 scale pan. At points, one beyond and one near the fruit, were 

 also two leaves which had attained their full size before the 

 experiment began, as was demonstrated by measurements of 

 their superficial extent. Thus the scale pan was freed from 

 the weight of all rapidly growing organs except the fruit, and 

 besides its weight variations, only those due to the transpira- 

 tion from the surface of two leaves and a portion of the stem 

 about 40 cm. in length were recorded by the apparatus. 



The fruit at the beginning of the experiment was 6 cm. in 

 diameter and weighed 138 grams. The latter fact was deter- 

 mined by weighing several fruits of equal size and also by 

 subtracting the net increase from the final weight at the end 

 of the experiment. 



3. Minn. Bot. Stud. Pt. i. 181. 1894. 

 4 Minn. Bot. Stud, Ft. 4. 179. 1894. 



