XXI. THE GRAND PERIOD OF GROWTH IN A 



FRUIT OF CUCURBITA PEPO DETERMINED 



BY WEIGHT. 



Alex. P. Anderson. 



Method of experimentation. Almost all of the available 

 information concerning the factors in the grand period of 

 growth has been obtained by experiments in which the rapidity 

 of growth has been determined by measurements of change in 

 form and size of the organs under observation. The work in 

 this direction abounds in results of great accuracy and in many 

 cases of extreme delicacy. These have been attained by 

 the use of the auxanometers of Baranetzky and Sachs, and 

 the perfected forms of such apparatus devised in the labora 

 tories of Pfeffer and Wiesner. Length-extensions have been 

 determined by use of the horizontal microscope (Detmer) or 

 telescope (Sachs), and increase in thickness, or in the shorter 

 diameter of organs by the micrometer apparatus of Darwin, 

 and the delicate auxanometers of Golden and Frost. 



From the great mass of material obtained by the experi- 

 ments in which these pieces of apparatus have been chiefly 

 employed, the influence of the principal external conditions on 

 growth-extension has been quite approximately ascertained. 



It remains yet to be seen however what correspondence 

 exists between growth -extension and increase in weight of an 

 organ, and how far the changes in weight may be taken in the 

 delineation of the curve of the grand period of growth. 



The use of weight as a means of measurement of growth has 

 been very limited because of the difficulty of obtaining the 

 necessary data at short intervals by reason of the con- 

 nection of the plant with the substratum, and the mechanical 

 difficulties in the way of obtaining the correct weight of organs 

 while attached to the plant. The work is still further compli- 

 cated by the constant changes in weight due to excretion and 

 transpiration. 



