OF TREE BRANCHES AT FREEZING TEMPERATURES 37 
in the case of large trees) that the movement begins when the 
temperature of the air reaches the freezing point of water. 
Two movements are described, a gradual seasonal displace- 
ment, and a secondary, depending indirectly on thermometric 
changes. Whether the latter is similar to the one to be described 
is difficult to ascertain. Ganong has performed some important 
experiments, and concludes that the secondary movements are 
correlated with changes in temperature but that they are not 
directly caused by temperature. 
Miss Jean Broadhurst * is the author of a note entitled, ‘‘ The 
weeping willow in winter,’ describing the observation that the 
slender unbranched twigs of this tree (twigs one to two feet 
long), which in November hang vertically, become curled up dur- 
ing the early winter so that the ends of the twigs are above their 
origin. The phenomenon appears to be a seasonal one rather 
60 ce ie Es BP 
joe Re aa 
Sb ee J a _ HEIGHT OF BRANCH 1 
é a. ae ae 
ne |z TreeNed ft 
40/9 1 Linden | 
i < a 
a \ Be Temperature F Li 
Ma [ 2 Be. a cn 
8 [I * A ie 
ia s 08% \ / ‘ Z cr’, 
eK K Gis TY 50 
X x ‘ « =I 4Q” 
"sé : 
<_ ra = 30° 
0 
65 Daily Record 2 | : 
SfeRe im 
oa : 
Sj + APRIL MAY an? 
60; 23 8 9 10 1 M15 1617 16 19 22 2% 25 297 301 2 6 13 25 wh 5 
Fic. 7. .Daily record of Branch B, Tree No. 1 (European linden) in April 
and May, in 1912, showing the same effect exhibited by Branch A, in Fic. 5, in- 
cluding the drooping in May due to the weight of the leaves. 
than one depending on temporary temperature conditions. A 
further note on the subject entitled, “‘Winter changes in the 
weeping willow,” was published later.t It is possible that the 
* Torreya 10: 38, 39. IQI0. 
+ Torreya 14: 31, 32. I914. 
