210 MorGcan: Hyporuests of FORMATIVE STUFFS 
buds that are less developed. But in the case of the roots, the 
second assumption would have to be reversed, since those that 
develop are the oldest root-buds. 
In this analysis I have attempted to give an explanation of the 
results without making use of the hypothesis of a directive flow of 
the formative stuffs, but it is clear that while the explanation may 
appear to hold for the shoots, it breaks down when applied to the 
roots ; and, I believe, that whatever form the hypothesis takes it 
meets with inherent difficulties. 
For example, let us take the application that Goebel has made 
in his attempt to explain the results of two different experiments 
with cuttings of begonia. He found that if his cuttings did not 
produce roots at the lower end of the stem, then the buds in the 
incisions of the leaves began to develop. He explains their de- 
velopment as due to the non-development of roots, and the con- 
sequent accumulation of some substance in the plant. But this 
will only account for the development of the roots of the plantlets 
on the leaves, and not for the leaves of the plantlets. 
Conversely, he found by removing all the buds from a plant 
that the buds in the incisions of the leaf began to develop. This 
again he explains on the hypothesis that those substances that are 
generally used up by the growing points have accumulated, when 
these parts have been removed. This might appear to account 
for the development of the leaf-buds in the incisions of the leaves, 
but not for the rootlets. The hypothesis proves too much.* 
My second question is this: May we not meet in these cases 
of regeneration with a phenomenon essentially similar to that 
which recent experimenters on the development of the non- 
fertilized animal egg have encountered? Contrary to the opinion 
first expressed, that the parthenogenetic development was due to 
the entrance of certain fertilizing ions into the egg, it has turned 
out that almost any kind of stimulus may start some eggs to de- 
velop. Such different kinds of things as salt-solutions, sugar, 
cold, heat, and even shaking will start the development of the egg 
of the star-fish. May this not be also the case with the piece of 
the plant? Will not any physical change affecting the germ start 
*It is taken for granted here that the shoot- and root-forming substances are dif- 
ferent. 
