ee cemita 
GOEBEL: REGENERATION IN PLANTS 205 
leaves of the foliaceous liverworts do not show any tendency to 
limit regeneration to the bases. This however is easily explainable 
from my point of view. These leaves are composed of only one 
or two layers of cells and so have at the time of separation neither 
a very large amount of constructive materials, nor definite con- 
ducting systems to carry them. They form adventitious shoots 
only when, after being cut off, they have been able to perform the 
photosynthetic processes for some time. No cause exists for the 
limitation of regeneration to the base of the leaf. The pieces 
from the flanks of the thallus of /zga/e//a behave similarly. 
On the other hand the leaves of Aryophyllum produce, in 
general, no new structures of their own when cut off, all of the con- 
structive material being used by the vegetative points already in 
existence in the indentations. The removal of these on a number 
of leaves caused the formation of roots at the base of the leaves, 
and in one instance of a bud also. These facts seem to lead to 
the conclusion that : 
1, The vegetative points serve as centers of attraction for the 
constructive material necessary for the formation of new organs. 
2. As long as the leaf remains attached to the stem the ma- 
terials flow into the stem; when the leaf is detached, the materials 
are appropriated by the vegetative points of the leaf. 
3. The removal of the vegetative points of the leaf is followed 
by the transfer of the place of origin of new structures to a point 
down the conducting tracts at the base of the leaf. 
The above are the chief conclusions so far attained, but much 
more research will be necessary before the processes of regener- 
ation are well understood. 
Mtnicu, November 15, 1902. 
[This paper was written in German ; the English translation, which was read at 
Washington and is here printed, while authorized by Professor Goebel, has not been 
revised by him.—Eb. ] 
