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Ig09] BORDNER—INFLUENCE OF TRACTION ON STEMS 255 
KLEIN (13) found the bundles more centrally located in the fruit 
stalk than in the petiole. He attributed this arrangement to the 
necessity for a greater mechanical strength, as well as for a more 
abundant supply of building material. 
DENNERT (5) compared the anatomical structure of the fruit 
stalk before and after the ripening of the fruit. He found an increase 
in the development of mechanical tissue. There was an increased 
amount of xylem anda greater thickness of the walls of the wood 
fibers. 
REICHE (24) investigated the transformation from flower to 
fruit stalk in many additional plants. His conclusions agree with 
those of the earlier investigators. 
PIETERS (23) showed that one-year-old fruit-bearing shoots of 
the apple and the pear had a smaller xylem cylinder in proportion 
to their diameters than the vegetative shoots of same age. They were 
well supplied with supplementary mechanical tissue, however, which 
was distributed at those points where it was most needed. In the 
case of the peach and the plum, the woody cylinder of the fruit-bear- 
ing shoot was larger than in the vegetative shoot. There was an 
abundance of well-lignified sclerenchyma and hard bast in the fruit- 
bearing shoots of the apple and pear, while in the vegetative shoots 
these tissues appeared only sparingly, if at all. 
GOEBEL (7, p. 206) writes: “Careful research demonstrates the 
existence of reciprocity between parts of the plant body... - . 
The size and construction of one organ are frequently determined 
by those of another.” : ; 
BoopLe (3) states that the walls of the sieve tubes and companion 
cells in Helianthus annuus become lignified as a result of strain. 
He also found a slight lignification of the parenchymatous 7 
of the pericycle and medullary rays, thus uniting the primary 
sclerenchyma strands into a more definite mechanical system attached 
‘o the strong xylem by the medullary rays. He says: “This must 
Sive greater rigidity, which no doubt is required by the heavy fruiting 
‘apitula borne by the plants.” 
KELLER (12) reached conclusions directly opposed to those 
teached by Boopte. He showed that a strong or light pull in the 
direction of the longitudinal axis of orthotropic flower stalks exerted 
