252 BOTANICAL GAZETTE [OCTOBER 
development of its mechanical tissue. In reporting the work of 
HEGLER, PFEFFER (21) says that a seedling of Helianthus annuus, 
whose original breaking strength was 160%", had a breaking strength 
of 250%" after two days under the pull of 150%". No breaking 
strength is given for a control. A petiole of Helleborus niger which 
withstood a weight of only 400%", PFEFFER reports to have held a 
weight of 3.5** after 5 days, during which time it had been weighted 
with a gradually increasing load, while similar petioles under normal 
conditions gained but little in strength. Changes are also reported 
in the anatomical structure: (1) an increase in the nimber of cells 
of the collenchyma, (2) an increased thickness of the walls of the 
collenchyma, sclerenchyma, and bast, and (3) the production of 
entirely new tissues. It is unfortunate that a full account of HEGLER’S 
methods and work was not published. 
HEGLER (10) showed that the phenomenon observed by BARANET” 
SKY and SCHOLTz was not purely physical, but that a physiological 
change took place within the cell, due to stimulation coming from 
the tension. As evidence, he demonstrated that when plants were 
dep~ived of oxygen or when they were under the influence of chloro- 
form, there was no response. He also found that the plants under 
tension were more turgid than controls, instead of less as ScHOLTZ 
had claimed. 
RICHTER (25) concluded that when the stems of Chara were 
subjected to a longitudinal pull, there was an increase in strength. 
BaLw’s criticism of RICHTER’s work is well taken. He says: “Di 
Resultate RicHTER’s sind etwas zweifelhaft; da er keinen Vergleich 
zwischen belasteten Chara Pflanzen und unbelasteten von demselben 
Alter und derselben Grosse gegeben hat.” ss 
Kuster (15) found no response, and showed that in the ie 
of Helleborus niger the new elements, which HEGLER (91) a 
were produced in response to tension, were there before tension? was 
applied. PFEFFER (22, p. 148) also found no response in the pro 
duction of mechanical tissue in plants subjected to tension. 
VO6CHTING (27) investigated the influence of tension on sunfl - 
and cabbages that had been prevented from flowering by se A 
decapitation. He found that no new tissue was formed, and that » 
increase in mechanical tissue occurred as a result of tension. 
owers 
