374 BOTANICAL GAZETTE [JUNE 
porting tissues. This shows itself in an increase in the amount of 
xylem and in the thickness of the cell walls of the same. 
B. INFLUENCE OF COMPRESSION ON STEMS 
In my experiments I made use of the following plants and seedlings, 
which were cultivated in the greenhouse: Helianthus annuus, Vinca 
major, Fuchsia speciosa, and Coleus tricolor. The controls were 
raised in the same place, and received the same care and attention 
as the plants under experimentation. 
A number of the above-named plants and seedlings, young and 
old, were subjected to compression by various means. The most 
common means was that of fastening the weights directly upon the 
stem. Around the stem, some distance above the ground, usually 
not more than 15°™, a strip of cotton flannel was wound. Over this 
and around the stem from opposite sides were noosed two loops in the 
manner already described in the tension experiments on Helianthus, 
Vinca, etc. Equal weights were attached to each loop, so that the 
strain was uniform on the opposite sides of the stem. To insure the 
stem from bending under the weight, bamboo stakes were driven into 
the ground close to the plant and then fastened to it in two places, one 
above and one below the place from which the weight hung, but so 
fastened as not to free the plant from the compression of the weights. 
In other cases the compression was narrowly localized. This 
regional compression was brought about in the following manner: 
Weights were hung from the sides of the stem as has already been 
explained. Below the attachment of these weights, some 10°™ dis- 
tant, a strong cord was fastened about the stem in the manner 2s 
described for the tension experiments. This cord was run over 4 
pulley fixed to"a support directly above, and to the distal.end of the 
cord were fastened weights equal to those hanging on the plant. 
By this method, a weight above pressing down and another below 
pulling up, there was a compressed region; while the upper and 
lower parts of the stem were free from compression. 
Variation in the method of hanging the weights on the plants was 
employed, but these details are of minor importance, and will not be 
given here. 
