1g2 BOTANICAL GAZETTE [MARCH 
leaves in the middle, surrounded by the fleshy petioles of the 
leaves the rest of which had been removed. Two of these 
petiole stubs were present, each reaching around far enough so 
that its edges lapped over one another. These petioles should 
execute any curving that occurs. I cut the end of the stub off 
square, and then split it into several slices, in such a plane that 
the upper and lower parts of the larger outer cotyledon were 
symmetrical, and placed the corms so that the split surfaces 
were horizontal. The atmosphere was unfortunately not satu- 
rated, and cutting and splitting the fleshy parenchyma gave 
such an opportunity for evaporation that in most cases after a 
week a shortening instead of an elongation had occurred. Nev- 
ertheless, a slight upward curve of each slice was noticeable, 
and a difference in their growth could be detected in spite of 
the shrinking. The following two experiments may represent 
the five made: 
1, Diameter of stub, 3mm, Cut into f qually 2, Diameter 35mm: jn five slices, Change in 
thick slices. Change in length of outer petiole sixjdays : 
in six days : Ist (undermost) slice. i 
Ist (undermost) slice. no change 2d . —— 
2d “ ney 3d “ —o.6™" 
3d “ =i. 4th _ “Ae 
4th #¢ pean, mm Sth “ —2,.0™™ 
It appears then that where these composite stem structures 
are split into a series of slices the growth of these is success- 
ively less from below upward. Some of these slices consisted 
(aside from the epidermis) entirely of the large celled cortical 
parenchyma, and seemed able individually to execute geotropic 
curvatures. Caladium is the only subject with which I have 
succeeded in getting a series of longitudinal slices of sufficiently 
equal thickness to give any kind of results. 
Helianthus. Nine hypocotyls of the “mammoth Russian”: 
variety were split, the cotyledons being either separated or split, 
and the split extending 1™ into the root. They were placed in 
horizontal glass tubes. After a day, four plants in which the 
difference in the growth of the halves was well marked were 
turned over, so that the halves exchanged places. 
