458 BOTANICAL GAZETTE [DECEMBER 
full of water alone was also taken at these temperatures. Finally 
the weight of the completely dried shavings was found. Now the 
specific gravity of dry cell wall substance is approximately 1.56, and 
the volume of saturated cell wall substance is nearly 3/2 that of dry 
cell wall substance. Then let a=increase in weight of pycnometer 
full of water from 32° C. to 6° C.; 6=increase in weight of pycnometer 
full of water and shavings from 32° C. to 6° C.; c=increase in volume 
of pycnometer from 32° C. to 6° C.; d=volume of pycnometer; 
e=volume of saturated cell wall substance; o.0046=expansion of 
1°° of water from 6°C. to 32°C. Then 
b+c—(d—e) (+) 
e€X0.0046 
= the ratio of expansion of cell wall to the expansion of water from 
6° C. to 32°C.7 Now, by substituting the values obtained in the 
experiment, 
; : +0.066 
0.4975 +0.066—(r00— 12,6) (2-438 +2:28%) 
=2.2 
12.6X0.0046 
=the desired ratio of expansion. 
PETROGRAPHICAL LABORATORY 
ARVARD UNIVERSITY 
}| 
© These are the figures given a Sacus, Hartic, and others, and used in comp — 
the tables of the Vermont Bulleti 
7 This formula would need a corrections for more exact work, ad “ 
accurate than the factors of specific gravity and volume of saturated cell wall. 
is more 
