362 : BOTANICAL GAZETTE [JUNE 
apparent, not only in the tensile strength, but also in anatomical struc- 
ture. On examination of various sections, HEGLER noticed (1) a 
numerical increase in the 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. These observations 
led him to the conclusion that a plant responds to a gradually increasing 
strain by a development of mechanical tissue. It is indeed unfor- 
tunate that only a preliminary report of HEGLER’s work can be had. 
The influence that his conclusions exerted has been widely felt, and 
the principles laid down were widely accepted. 
RICHTER (794) concluded that when the stems of Chara were 
pulled longitudinally, there was an increase of strength. Thus, in 
his opinion, he confirmed the observations and results of HEGLER. 
But we may dispose of this interpretation in the words of BALL (:04), 
who says: “Die Resultate RicHTERS sind etwas zweifelhaft, da er 
keinen Vergleich zwischen belasteten Chara-Pflanzen und unbelaste- 
ten von demselben Alter und derselber Grésse gegeben hat.” 
Von DerscHau (’94) came to the conclusion that a gradually 
increasing pull without contact on certain twining petioles raises the 
breaking strength, increases the development of mechanical tissue, 
and calls forth the development of new tissue. His first statement is 
borne out by experiments which show that even after twenty-four 
hours the plant part under strain could withstand a weight which at 
first would have broken it. From a study of sections of the various 
petioles, he found that marked anatomical differences occurred. 
There was a numerical increase in almost all kinds of cells. The 
bast thickened in all the petioles examined except those of Solanum 
jasminoides, and the ring of vascular bundles was made complete in 
all but Solanum, where it was half-moon shape, as in the normal 
petioles. 
Concerning tendrils no experiments have been recorded to deter- 
mine the effect of pull alone on the free basal portion. PENHALLOW 
(786, p. 49) noted that tendrils that had secured attachment were 
larger, stronger, and more rigid, from which it would appear probable 
that contact produces a more or less marked effect in accelerating OT 
at least in increasing the strength of parts. This view gains strong 
confirmation from similar conditions in Ampelopsis. 
