254 BOTANICAL GAZETTE [OCTOBER 
drils of the Cucurbitaceae; but he did not consider tension as a 
probable factor along with contact. , ; 
Worcitzky (30) reports that tendrils of Passiflora quadrangularis 
which had grasped a support broke at 600%", while the controls broke 
at 350%". With tendrils of Cucurbitaceae, the uncoiling resistance 
was thirteen times as great in those which had grasped a support. 
There was also a marked anatomical change; viz., a lignification of 
the pith parenchyma, which he assigned to no cause. 
Von DerscHau (28) found that a gradually increasing pull on 
certain twining petioles raised their breaking strength and caused 
an increased development of mechanical tissue. He found a nu- 
merical increase in almost all kinds of cells. The petioles of Solanum 
jasminoides showed the least response. ; 
NEWCOMBE (19, p. 446) says, in speaking of the reaction of tendrils 
to contact: “The first strengthening tissue is here laid down as 4 
Tesponse to contact; its increase is the regulatory response of the plant 
to the strain that it feels.’ See 
MacDoveat (17, pp. 377, 378) believes that contact stimuli oe 
not transmitted beyond 2 or 3™™. Since the thickening of the wee 
always takes place after contact, the natural conclusion would be tha 
this thickening of the tendril is due to the traction exerted by the 
weight of the stem supported by it. ee fe 
PEIRCE also (20, p. 241) believes that the strengthening © 
free basal portion is not due to contact. iin 
FITTING (6, p. 476) has demonstrated that contact stimuli ee 
transmitted to the basal portion of the tendril, and that therefore . 
effect of contact stimuli on the basal portion of tendrils cannot 
. excluded. 
5. CORRELATION 
The factor of correlation has been investigated by eget 
workers. Since self-regulatory development may imply 4 " of 
degree of correlation, it seems desirable that at least a brief review 
the work on correlation should be given. : cture 
Laporte (16) found decided differences in the anatomical =~ 
of the floral axis compared with the rest of the plant: (1) 22 (3) 8 
of bast, (2) a decided modification of the main bundles, and (3 
decrease of pith. 
