258 BOTANICAL GAZETTE [ocTOBER 
no increase of mechanical tissue in the sunflower stems, and but a 
slight increase in the cabbage stems, an increase not at all propor- 
tional to the weights used. 
HripBarD suspended weights upon the stems of the sunflower, 
periwinkle, fuchsia, and coleus, and found in all except coleus a slight 
response to compression by self-regulatory increase in mechanical 
tissue. He did not believe, however, that the evidence could be 
regarded as conclusive. 
BicHeEr inclosed both the upper and the lower portions of stems 
of the castor oil plant in plaster casts, and then fastened these 
casts so that the stems as they elongated were subjected to a longl- 
tudinal compression. All but two of his plants became bent; 
the two which remained straight were weaker in mechanical tissue 
than normal plants. ; 
From the few data which have been recorded, it is very plain 
that we do not have sufficient evidence to show whether or not 
compression or increased weight may act as a stimulus to cause the 
production of a greater amount of mechanical tissue in plant stems. 
General conclusions have been drawn from mere observations of 
phenomena, which may be due to any one of several influences 
or to the combination of two or more influences. , The few expett- 
mental data have led to indefinite or contradictory conclusions. 
This investigation was undertaken to secure exact experimental 
data upon the effect of weight tending to produce a longitudinal 
compression in vertical stems. 
Materials and methods 
PLANTS USED 
From the nature of the experiments, it was necessary to use 
plants with single upright stems. Both woody and herbaceous 
plants were used. The woody plants were both one-year-old 
shoots and seedlings of the common locust (Robinia Pseudo- 
Acacia), both young and one-year-old shoots of sumach (Rhus 
glabra), one-year-old shoots of the poplar (Populus tremuloides); 
and the castor oil plant (Ricinus communis). The herbaceous 
plants were the sunflower (Helianthus annuus), the broad or 
Windsor bean (Vicia Faba), and the common bean (Phaseolis 
