Anderson: growth of cucurbita. 275 



the balance, and the position of the stem between the fruit and 

 the point of support remained as before. 



The leaves near the fruit had been cut away so that the fruit 

 formed the only weight on the balance. From 10 a. m. to 

 2:30 P. M. a decrease of three grams occurred. From 

 2:30 p. M.. November 2, to 4:30 P. M., November 3, there was 

 no change in the weight of the fruit. All this time, however, 

 as shown by the psychrometer, transpiration was rapid. The 

 stem in the beaker absorbed twenty-three cubic centimeters of 

 water, which must have been taken up by osmotic action and 

 transpired by the fruit. 



At 4:30 P. M., November 3, the fruit was separated from its 

 stem and placed on the decrease pan of the registering bal- 

 ance, whore it remained until 10 a, m., November 7. While on 

 the decrease pan the fruit showed a daily periodicity in its loss 

 of weight, this being greatest at the time of least relative 

 humidity. 



The amount of daily loss in weight became less each day with 

 the drying of the rind and the cuticularization of the epidermis. 



The use of weight as a means of measurement of the rapidity 

 and amount of growth of massive organs is found to be a fairly 

 efficient method in the determination of the features of the 

 daily period and the grand period. The changes in weight 

 due to conditions of transpiration and accession of food mater- 

 ial are such that their periodicity corresponds to that of 

 growth. 



The conditions of transpiration and their effect in such ex- 

 periments are easily controlled and analyzed, and a curve of 

 the growth may be plotted, which would be entirely free from 

 error arising from this source. 



The curve representing the growth of a plant, determined 

 by weight, will be found approximately correct, although of 

 course both the upper and lower apices of such a curve will be 

 somewhat extended. On the other hand, in auxanometric 

 measurements of length-extension only one dimension of an 

 organ is taken into account, and the error in such instance 

 must be equally great, and is, moreover, incapable of elimin- 

 ation. 



SUMMA.RY. 



1. The grand period of growth of the fruit of Cucurbita 

 under observation occupied 34 days. 



2. The growth of this fruit took place in a temperature 

 varying from 4''C. to 28°C., and in a humidity from 50 to 98 per 

 cent. 



