390 BOTANICAL GAZETTE [JUNE 
To determine the exact amount of contraction the Zeiss cover- 
glass measurer was used. . Pieces about 10°™ long of one or two 
year old twigs taken at—18° C. were inserted in the clamps of the 
machine, a record taken, and then the whole carried to the warm 
laboratory. The increase in size on thawing could be followed 
by watching the movement of the indicator as the ice melted, and 
when at last stationary another reading was taken. Some results 
are given in the following table: 
: Frozen Thawed Difference Exp. or contr. 
Cormis etolodifera < 00.25% 62. 4.3 2.58mm/ 2, 60mm o.o2mm| expanded 
he oF i oP se acs Eire ares 3.38 3-43 0.05 i 
"EWR QUGIYDNGUOS Soa ee 2.03 2.10 0.07 si 
- Feces ok cath gare. tovalvee sid 3.18 3-39 O.12 i 
Pennies Mlstates 66. Peony os 5: 3-17 3.28 O.11 
" ee We is © pe ee gk 4.72 4.80 0.08 i 
Acer piataniless yee kat 2.82 2.86 0.04 ig 
Oe es gare hgh as 3.44 3.48 0.04 = 
Pyrus Malus......... 0.2.0.6... 2.97 3.03 0.06 # 
WANES Set. yas a arate 3.89 ze 2 0.06 
ale MORO Gare nce diy es & 94 5.4 0.10 is 
pee ne) Sit a ee eS: 5-9 0.14 . 
Many twigs at — 18° C. or below appear very much wrinkled on the 
surface as though dried and dead. This is especially true of the 
polished shoots of Salix cordata. On very cold mornings shoots 
of this species appear as though dead and dry, the bark being com- 
pletely covered with fine longitudinal wrinkles. Some of these 
shoots were brought to the laboratory and allowed to warm, during 
which process the disappearance of the wrinkles could be watched 
with ease. In about ten minutes the twigs were entirely smooth 
and normal. It was from such twigs that the above readings were 
taken. To show more graphically the expansion during thawing, 
some twig-sections about 10°™ long were taken from the same willow 
and the ends while still frozen dipped in melted paraffin. The 
caps thus produced at the ends of the twig were in every case rup- 
tured down the side on thawing, leaving in most cases a cleft of 
considerable size between the two edges. Twigs of plum were 
bei dem Gefrieren u. Veranderung der Zellhiute bei dem Aufthauen saftiger Pflan- 
zentheile. Bericht Verhand. Konig. Sachs. Gesell. Wiss. Leipzig, Math.-Phys. Klasse 
12:1-50. 1860. Mirrer-Taurcav, H., Ueber das Gefrieren und Erfrieren der 
Pflanzen. Landw. Talnb. 9:187. 1880. 
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