196 BOTANICAL GAZETTE [MARCH 
pairs of plants were treated in the same manner. In three days 
the average growth was: 
Of ten erect halves - . - - - - - 15.725 
Of corresponding horizontal halves, split surface down - 13.9™™ 
Of other ten erect halves - - - - - - 12,35" 
Of horizontal halves, split surface u - - - + 2ene 
Or, calling the growth of the erect halves 100, that of the hori- 
zontal halves with split down was 88.5; that of horizontal halves 
with split up, 178.9. 
The growth of the isolated under half then is decidedly 
accelerated, while that of the upper half is in a lesser measure 
retarded. Sachs® long ago showed that this happens when an 
entire stem executes its response to geotropism, and it is inter- 
esting to note that isolation of the halves does not affect the 
quality of the reaction at all. This ought to give the quietus to 
all of the various theories which would explain the execution of 
the geotropic response by processes taking place entirely in 
either half. 
The behavior of split stems emphasizes the fact that geo- 
tropic irritability is dependent upon the relative positions of the 
tissues of the stem: and seems to me to point toward a more 
intimate connection of the perception of the stimulus with the 
execution of the response than we have hitherto felt justified in 
assuming. The execution of the response by whole stems does 
not demonstrate any transverse transmission of a stimulus by 
which the halves compare their positions, for the behavior of the 
Separate halves shows that no comparison is required. 
UNIVERSITY OF WEsT VIRGINIA, 
Morgantown. 
aufwarts krummender Sprosse. Gesammelte Abhandlungen 2:945. (From Arb. des 
burg 1:193. 1872). On P- 955 he says: “Bei der Aufwarts- 
, konvexen Seite stirkes, der der oberen, kon- 
: cher als die gleichnamigen Gewebestreifen eines aufrechten Sprosses 
in derselben Zeit,” 
