258 BOTANICAL GAZETTE _ [ocroser 
materials from the leaves would be stronger toward this point than 
toward the tuber of any other point in the plant. There seems to 
be some factor dependent on the presence of growing tubers or bulbs 
which prevents the fertilized embryos from developing even in the 
presence of sufficient food and moisture. Kindred phenomena are 
common, é. g., the death of the fern prothallium with the developing 
of the embryo. This cannot be due primarily to starvation, since 
each cell retains its own mechanism for food manufacture. 
MorGAN (II, p. 272) has suggested that these phenomena are 
due to differences of tension existing throughout the plastic parts of 
the plants. “As long as the apical bud is present at the end of 
the stem or branch, or even near the apex, it exerts a pull or tension 
that holds the development of the parts in check; but if the apical 
bud is removed, the tension is relaxed and the chance for another 
bud developing is given.” And further, Morcan suggests that 
“from the apex of the plant to its base the tension is graded, being 
least at the apex and increasing as we pass to the base,” so that, 
when the apex is removed, ‘those buds will develop first that are on 
the region of least tension, and then development will hold in check 
the other buds by increasing or establishing the tension on the lower 
part of the piece.’’ Just what this “tension’”’ may be is not very clear, 
and with GorBeL I am unable to see that it makes the matter any 
plainer. Morcan has suggested later (12) that if this idea of differ- 
ences in tension is too vague, it can be given a more practical form 
by assuming it to be the outcome of osmotic differences in the cells. 
Diligent search has failed to reveal these in Salix or Phaseolus, and 
there seems to be no basis for the assumption. 
Morean has more recently modified this hypothesis by another 
Suggestion (13), according to which the difference in the develop- 
ment of buds at the two ends of a piece of stem is due to the relative 
state of development of the buds. In the willow, for example, those 
toward the apical end have reached a greater’ degree of matunity 
than those lower down, and so naturally are the first to develop. 
A few experiments will show this hypothesis to be quite untenable. 
Experiments already mentioned have indicated that when We taxe 
two pieces approximately alike, and remove all except the ‘be 
buds from one, these buds will develop simultaneously with 
