1906] WIEGAND—BUDS AND TWIGS IN WINTER 393 
| Frozen Thawed Difference oO +e ed 
| eae) er een 
Cornus stolonifera............ | 2.22mm 2,20mm 9.02mm | contraction 
a“ SO veg fal NS Chote l= 2860 2.61 0.05 a 
Tilia platyphyllos.......... 3.63 3.54 0.09 i 
Pim. Tres dais okie *.i5 3.07 0.08 S 
Populus dilatata.... «20.66 ..04. | 2.97 ey | ©.00 ° 
PS eet eT roe fae 2.03 3.04 0,01 expansion 
Acer platanoides............. 5.06 5.08 0.02 - 
iy cody emai S ee 4-34 4-34 0.00 s 
“s pa rete Pe 4.16 4-17 0.01 = 
ie a | ea ae as 4-92 4.88 0.04 contraction 
“ee se ae 
is Bo eRe Pee het ag eee 4.04 4-03 0.01 - 
eee ee 4.92 4.68 0.04 : 
Prunus persica............... 2.62 2.59 0.03 ' 
* Sige Te Te 2.50 2.46 0.04 . 
‘a POD alte Sete ies 2.72 2. 66 0.06 . 
Prunus americana............ 2.17 2.09 0.08 
s Meee ree ee 1.78 Ei71 0.07 ie 
ve fe he ec or ae 2.10 2.06 0.04 “ 
the wood is eliminated, of course, and that the formation of ice tends 
to bow out the scales so that they stand less closely together. If 
the bud scales curve like leaves in freezing this result is to be expected. 
When the temperature rises sufficiently, the buds and twigs thaw 
out and regain their normal condition. In the sections under the 
microscope the reabsorption was so rapid as in most cases to be 
entirely completed when the ice itself had finished thawing. This 
results in an active sponging-out movement in the sections as 
the cells recover from their collapsed condition (fig. 6). On account 
of the rapidity it is frequently difficult to keep the point of observa- 
tion in the field of the microscope. Thawing seems not to harm 
these tissues in the least, no matter how frequently or how abruptly 
it is done. I have often tried the experiment of transporting twigs 
abruptly from —18° C. to the warm laboratory at 21° C. and back 
again several times, thus alternately thawing and freezing them. 
No matter how many times this was repeated no injury could be 
detected in the buds, even when subsequently placed in the green- 
house to grow. 
Buds and twigs do not thaw at o° C. if the rise in the surrounding 
temperature is gradual, as it is in atmospheric changes, but at a 
much lower degree. The thawing like the freezing is proportional 
to the temperature, and is almost if not quite completed when the 
