294 The Botanical Gazette. — (July, 
netzky registering auxanometer. The curves of both plants 
were plotted together for comparison. Shoots, petioles and. 
seedlings of the following plants were used. Helianthus an- 
nuus, Helianthus tuberosus, Phaseolus multiflorus, Tropaeo- 
lum majus, Tropaeolum minus, Ricinus bipinnatus, Linum 
usitatissimum, Cannabis sativa, and Dahlia variabilis. 
By a series of experiments, using weights of 20-150™ 
the conclusion is reached that the retardation of growth is to 
be regarded as a typical irritation phenomenon. An acceler- 
ation of growth takes place as soon as the weight ceases to 
act as a stimulus; but a new retardation can be produced by 
upsetting the equilibrium by an increase in weight. 
I. The amount of weight necessary to produce a retarda- 
tion varies in the same individual. Weights of 1.3-5%™ are 
sufficient to call forth a response in some plants, but others 
require still larger weights. 
Ill. The retardation produced by traction is the greatest 
at the beginning of the grand period, diminishes towards the 
maximum, where it is almost nothing, and again increases as 
we descend the other arm of the curve. Large weights 
(150) call forth a retardation even at the maximum of the 
grand period. cee 
IV. The same is true for the daily period. If the eer 
bility at the daily maximum is very low, the weight whic 
before called forth a retardation, here produces an ee 
tion of growth. Whena weight which has upset the equili 
rium remains constant, the change of stimulus gradually 
ceases to work and to give place to the mechanical effect. 
A diminution in the weight also produces a retardation. 4 
retardation then is dependent upon the abrupt change 
weights, either an increase or a decrease. a 
V. By using etiolated specimens, the daily periodicity tain 
avoided, when the retardation was not inhibited at eh 
phases but remained regular. The etiolated specimens W 
very sensitive to the weight as a stimulus. 
I. The approximate proportion given by Scholtz 
the acceleration and the number of days is an inver tion. 
portion between the weight and the amount of acceleratt’ 
For the same number of days the acceleration 
the increase of weight and passes with the hig 
second to fourth day to a retardation of growth. 
VII. A new retardation may be produced by a 
decreases W! 
‘iar = : 
between 
h weight inthe | 
spontane 
