278 BOTANICAL GAZETTE [OCTOBER 
If, on the other hand, we take the meaning in the general sense, 
that a plant responds to the demands (‘‘das Bediirfniss”) made 
upon it, we may interpret the phrase to mean that he fastened 
the weights in such a way as to simulate the tension caused by 
the fruiting head. Bicuer (4) interpreted this to mean a longi- 
tudinal pressure or compression, as indeed it must if the fruiting 
heads remained erect. Since, however, the fruiting head of a 
sunflower droops, it must exert tension upon the part of the stem 
next to it, and both tension and compression in the bent part, 
tension upon the upper or convex part and compression upon the 
under or concave part. It seems from a later statement of VOcH- 
TING’s that the stems were kept erect. In that case, the “Belas- 
tung” must have exerted a compression only. He says in summing 
up his results: 
Wir fanden, dass selbst sehr starke Belastung der aufrechten am Bliihen 
verhinderten Objecte nicht geniigt, um das normale Holzwachsthum wieder 
herbeizufiihren. 
Bucuer found weaker development of the mechanical tissues 
and less cambial activity in the two castor oil plants which he 
subjected to longitudinal compression than‘ in normal plants. 
The stems were also larger in diameter, owing to the abnormally 
large thin-walled cells. 
Hrsparp (14) used the same general method for subjecting 
stems to compression that I have employed in this investigation. 
His experiments were of a preliminary nature, comparatively 
few plants were used, and there is no record of his making mechan- 
ical tests or exact measurements of the mechanical tissue. When 
so few plants are used and no averages made, errors from indi- 
vidual variation may easily occur. It is not certain that the 
possibility of personal error was eliminated, although he says that 
the same conclusions were arrived at by two persons working 
independently. 
In reference to H1pparp’s experiments as well as to my OW”, a 
question may arise as to whether a stimulus:is really exerted by 
such means as were used. This question may be answered 10 
several ways. It is well known that living protoplasm — 
sensitive. This sensitiveness is shown by the responses of Mimosa 
