STUDIES IN PLANT REGENERATION 219 
they possessed both the tuberous swelling and roots (Fig. 10, с). 
And, as a climax one leaf has been discovered in which neither the 
roots nor the swelling appeared, but an actual tuber on which 
buds are visible (Fig. то, 4). All these leaves were taken from 
the same plant and subjected to apparently identical conditions. 
Experiment 34.— When the petiole of a leaf is largely or 
entirely cut away, roots form additionally or solely from the under 
side of the lamina. This occurs, for example, in Begonia Cred- 
пет, Peperomia argyrea, Iresine Herbstu, etc. Roots may also be 
called forth by extra transverse cuts in the blade, and in Exuphor- 
bia nivulia by longitudinal cuts. Parts of leaves used as cuttings 
behaved just like those described by Vochting and his predeces- 
sors; butin no case was an isolated petiole found to form shoots. 
Experiment 35. — To determine whether leaves had any power 
of rooting from the apex, the tip was removed from blades of vari- 
ous species of Begonia, Echeveria, Sedum and Pelargonium, and 
from Bryophyllum leaves from which the buds had been cut out, 
and the leaves were planted with the apical end down. Іп order 
to prevent evaporation from the exposed end of the petiole, this 
was covered with paraffin. Some of the leaves remained turgid 
for five months, but none ever rooted in this position. 
The abnormal increase in the size and thickness of regenerat- 
ing leaves has been noticed by DeVries * and Lindemuth,+ and 
has recently been worked out in careful detail by Mathuse. The 
same phenomenon attracted the writer's attention and measure- 
ments were being taken when Lindemuth's paper appeared. His 
results and Mathuse's fail to confirm a statement made by DeVries 
that the life of a leaf when planted is not noticeably prolongec 
beyond its duration on the parent plant. Lindemuth's rooted 
leaves in some cases lasted five years and were then sacrificed for 
*DeVries, H. Über abnormale Entstehung secundarer Gewebe. Jahrb. wiss. 
Bot. 22: 35. 1891. 
fLindemuth, H. Uber Grosserwerden isolierter ausgewac 
ihrer Bewurzelung. Ber. Deut. Bot. Ges. 22: 
iMathuse, 0. Über abnormales sekund 
Bot. Centralb. Beiheft. 20 : 174. т 
hsener Blatter nach 
171. 1904. 
fires Wachstum von Laubblattern, etc. 
