364 BOTANICAL GAZETTE [JUNE 
experiments to determine exact conditions, he has been able to show 
that in general the breaking strength of a plant stem does not increase 
in response to a gradually increasing pull, and that no increase of 
breaking strength follows as a result of pull on a stem growing in a 
horizontal plane. Detailed examinations of microtomic and free- 
hand sections, stained and unstained, show that there is, as a result 
of pull, no increase in the thickness of the walls, nor a numerical 
increase in the cells of the various tissues. No new tissues are pro- 
duced as a result of the strain. A number of other authors, KUSTER 
(p. 173), PFEFFER (:01, p. 148), and V6cHTING (p. 282), have also 
failed to detect or observe any production of new tissues. 
The factor of correlation has yet to be briefly mentioned. It is 
generally admitted by writers who have investigated the subject 
that a very high degree of correlation is manifest between the various 
organs of the plant. GorBEL writes in his Organography oj Plants 
(p. 206) “that careful research demonstrates the existence of recipro- 
city between parts of the plant body... . . The size and construction 
of one organ are frequently determined by those of another.” 
KLEIN (’86) showed that the bundles were more centrally located 
in the fruit stalk than in the petiole, and attributed this arrangement 
to the necessity for a greater mechanical strength, as well as for a 
more abundant supply of building material. 
DENNERT (’87) on comparing the anatomical structure of the fruit 
stalk, before and after ripening of the fruit, found an increase in the 
development of ‘mechanical tissue. This was apparent in the greater 
increase in the xylem and in the thickness of walls of the wood fibers. 
REICHE (’87) corroborates the work of the earlier investigators 
and shows in many additional plants that changes in the flower stalk 
during its transformation to a fruit stalk go hand in hand with the 
development of the fruit. 
PreTERS.(’96) showed that although one-year-old fruit-bearing 
shoots Of the apple and the pear had a smaller xylem cylinder in pro- 
portion to their diameters than the vegetative shoots of the same age, 
they were well supplied with supplementary mechanical tissues which 
was distributed at those points where it was most needed. In the case 
of the peach and the plum, the woody cylinder was larger in the fruit- 
bearing shoot than in the vegetative shoot. Fruit-bearing also 
