THE DIGESTION OF STARCH IN GERMINATING PEAS 1 



VV. RALPH JONES 

 Department of Agriculture, Washington, D. C. 



Rywosch 2 has called attention to the fact that when a pea is 

 germinated, the disappearance of the starch content is not simul- 

 taneous in all parts, but usually takes place in a regular cell 

 succession, beginning in the peripheral cells and passing inwards 

 toward the vascular bundles. He has pointed out that when the 

 starch in the peripheral layer of cells is dissolved, the osmotic 

 pressure of these cells must be raised, and the sugar produced 

 should diffuse inward into the adjacent cells where the osmotic 

 pressure is lower. This diffusion should continue until the vas- 

 cular bundles are reached, and the sugar is conducted away from 

 the cotyledon. 



In an attempt to gain more definite information toward an 

 explanation of this striking phenomenon, a series of experiments 

 was carried on during the spring of 1910, in the Laboratory of 

 Plant Physiology of the Johns Hopkins University. The work 

 was undertaken at the suggestion of Prof. Burton E. Livingston, 

 to whom I am greatly indebted for his constant interest and his 

 helpful suggestions. Although little definite knowledge of the 

 causal factors here involved has been obtained from these experi- 

 ments, yet considerable advances have been made toward that 

 dynamic appreciation of these processes which is fundamentally 

 essential to their physical interpretation. 



Ordinary dried peas were used for the main part of the study. 

 These were soaked in water and then germinated, and allowed to 

 grow in moist sand, or on moist filter paper in a moist chamber 

 in darkness. Hand transverse sections of the cotyledons were 



1 Botanical Contributions from the Johns Hopkins University, No. 29. 

 2 Rywosch", S., Uber Stoffwanderung und Diffusionstrome in Pflanzenorganen. 

 Zeitschr. fur Bot, 1: 571-591. 1909. 



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