Anderson: GROWTH OF cucurbita. 239 



In the following experiments the first difficulty was overcome 

 by the use of the registering balance which I have described 

 in a previous number of this bulletin. ^ 



In order to lessen the mechanical difficulty of obtaining the 

 correct weight of a portion of a plant while still in organic 

 union, the fruit of Cucurbita pepo was selected because of its 

 rapid growth and relatively large size and weight, and the 

 slender somewhat pliant stem on which it is borne. By reason 

 of this latter fact the weight of the fruit could be ascertained, 

 while the error resulting from the bending of the stem remained 

 the same in the swing of the scale pan through an arc of two 

 centimeters, and was so nearly constant throughout the experi- 

 ment that it offered no disturbing factor in the general results. 



A still further reason for the selection of this material was 

 the fact that F. Darwin had made a series of observations on 

 the fruit of Cucurbita in a similar manner. His experiments 

 were begun when the fruit had nearly reached the maximum 

 rate of growth and included only a portion of the grand 

 period. ^ 



In the experiments detailed on the following pages it was 

 purposed to follow the changes in the weight of the fruit from 

 the time when its mass was first appreciable by the balance, 

 through its stages of growth to maturity, with attention to 

 its changes during the "ripening" period. An effort was made 

 to analyze the relations between the changes in weight of 

 the fruit with the transpiration from its own surface as well 

 as from the remainder of the plant. This latter purpose en- 

 tailed numerous and frequent observations of the light and 

 humidity as well as other atmospheric conditions. 



To obtain suitable material under normal conditions, seeds 

 of Cucurbita pepo were placed in a plot of sandy loam immed- 

 iately on the south side of Pillsbury Hall, May 24, 1894. On 

 September 20 several plants had obtained the length of 9 

 meters with a strong development of leaf surface. 



The terminal portion of one of these vines, 1.5 meters in 

 length was taken into a laboratory room by an aperture in the 

 sash at a point 7 meters from the root. The part of the vine 

 remaining in the open air carried a leaf surface of about 3.5 

 square meters and branched somewhat profusely. The labor- 

 atory was fitted with a solid wall tible next the windows on a 



1. Minn. Bot. Stud. Part 4. 177. 1694. 



2. On the growth of the fruit of Cucurbita. Ann. Bot. 7 : 459. 1893. 



