394 BOTANICAL GAZETTE [MAY 
IN HIS PAPER on causes governing the direction of branch growth Baran- 
etsky 33 presents some new results of experimentation in this field. The author 
used entire plants, a number of woody and several herbaceous species being 
brought into requisition. The stems and branches were first bent into vari- 
ous positions and held thus until a geotropic growth curve had resulted, after 
which the plants were freed and placed upon a revolving klinostat. One of 
the most important results of the study of these rotating plants is the dis- 
covery of what is termed “opposite bending.” By this the author means that 
phenomenon wherein the plant not only straightens a previously formed geo- 
tropic curve, but passes the original vertical position and bends in the oppo- 
site direction. After the first opposition curve is formed, a return to the 
_ Original curvature may result, giving a pendulum-like motion of the tip, 
which exhibits several vibrations of gradually decreasing amplitude, until at 
length the normal position is reached. Such curving is ascribed to an accel- 
erated growth on the concave side, of sufficient vigor to throw the tip beyond 
a its first position. This then stimulates growth on the new concave side, but 
with lessened intensity, thus producing the vibration just noted. In his’ 
_ explanation of this opposition curve Baranetsky differs from Véchting and 
Czapek, who hold that the increased growth on the concave side is merely 
_ sufficient to return the tip to its original position. Baranetsky also suggests 
tha: owth on the concave side may be aided by an inhibition on the convex 
due to stretching of the cells. 
Baranetsky carried on observations in the field as well as by laboratory : 
periments, The forms studied are divided according to their behavior 
‘into three types: the Prunus type includes Aesculus and Euonymus Soe 
linden type includes Ulmus, Fagus, Crataegus, Celtis, and Corylus ; 
eedle-leaf type includes the pines. The first group is characterized 
al Dior states the four following points : (1) physiological ! 
t (2) lateral shoots behave as main shoots; (3) all shoots — 
1 ; and (4) each curve produces an opposition curve ee _ 
essen or overcome the geotropic curvature. For the second ae 
