ala 
1905] MCCALLUM—REGENERATION IN PLANTS 257 
those that induce growth everywhere), but the cause of non-develop- 
ment in the normal life of the plant; and this seems to lie in that 
influence which one part may exert over other parts or throughout 
the entire plant. A glance will show how universal this is among 
plants and the variety of ways in which it may manifest itself. If 
the main shoot of spruce is cut off, one or perhaps more of the dor- 
siventral plagiotropic lateral shoots will change their nature and 
become erect and radial. Many bulbous and tuberous plants do 
not produce seeds normally, but if the bulbs or tubers are removed 
seed production is then accomplished. This cannot be explained 
on the ground of specific bulb and seed forming substances, since 
if we assume the existence of these two substances, we must assume 
them to be different. GorBEt (3, p- 213) says “‘in the normal 
condition the seed formation is hindered because the plastic material 
which might be used for the seeds streams into the bulb, where it 
is turned to account in the formation of bulbils for asexual repro- 
duction.” The assumption is that the nutritive materials, stream- 
ing to the point where the bulbs or tubers are to be formed, incite 
the formation of these organs; and if these are prevented from 
forming, the material will flow toward the flowers and there stimulate 
seed formation. This supposition is exactly the opposite of what 
nig tually occurs in plants. The nutritive, or any other soluble material, 
diffuses from its point of greatest density in all directions, as well 
toward the seed as toward the bulbs, and it will diffuse in one direction 
rather than the other because it is there being either changed or 
“moved from solution by the activity of the cells. ‘The “streaming” 
does hot start the growth, but the growth activities remove the 
7 oopetimaldihetgr ete teon =~ 
cell activities in lvi : saat . i 
volving a use or change of material must of necessity 
Sage any movement other than diffusion in all directions. We 
: reason for assuming that the food made in the leaves would 
hia the bulb any faster than toward the seed, and oes 
a. A ant in a well-nourished condition it is scarcely possible 
ount available would be so slight that the embryos would 
Still be 
even eee 4 condition of starvation so extreme that they could not 
8 . 
art to grow. If the latter were true, the diffusion of food 
