346 Curtis : The Work Performed in 



lucida. The weight of the areas bearing the tracings of the wood 

 sections having been determined, by cutting out the lumen of the 

 cells and determining their weight, the percentage of cavity could 

 be determined. This appears to be fairly accurate. The tinfoil 

 selected showed but slight variations in weight and the tracings, 

 cutting and weighing can be made with accuracy. In the follow- 

 ing experiment with Acalypha a potted plant was placed in a glass 

 jar and the mouth of the jar covered so as to prevent evaporation 

 from the soil. The amount of transpiration for two hours was 

 found to be at the rate of 7. 1 grm. per hour. The stem was then 

 cut under water and allowed to stand three hours. It was then 

 allowed to absorb water from a florence flask plugged with cot- 

 ton for two hours, the loss per hour being 4.53 grm. The 

 stem being transferred to a solution of eosin for one hour the 

 ascent of the fluid was found to be 75.4 cm. From cross sections 

 of the stem the following area of lumen and percentage of cavity 

 was obtained : 



Weight of area adjoining pith 3-030 



i i 



11 cavity in this area 1. 726 Percentage of cavity 56.9 



Weight of area in middle of xylem 3.047 



M " cavity in this area I- 709 Percentage of cavity 56.1 



Average 56.5. 



The area of the cross section of the stem was 23.15 sq. mm. 

 This would give a water conduit of 13.08 sq. mm. 



It is interesting to note the relation of this latter area to the 

 rise of eosin in the stem and the absorptions both in the case of 

 the cut and uncut stem. Taking the rise of the eosin, 75.4 cm. 

 as an approximation of the rate of absorption of the cut stem it is 

 seen that only 6.01 sq. mm. would be required to carry 4.53 

 grm. to a height of 75.4 cm. Considering the absorption of the 

 uncut branch if the entire area at the disposal of the stem for the 

 conduction were utilized the 7.1 grm. would rise only 54.2 cm. 



Two similar tests were made on Abittilon. The potted plant 

 transpired 3.25 grm.; cut, 2.95 grm. per hour. Percentage of 

 cavity, 50.1. . Area of wood, 37.75 sq. mm. Area of cavity 

 18.91 sq. mm. 3.25 grms. would consequently rise 17.18 cm. 

 if entire area was utilized. Recorded rise of eosin, 23.5 cm. This 

 would require an area of 13.84 sq. mm. 



