436 BOTANICAL GAZETTE [NOVEMBER 
showed a varying pressure ranging from 0.1 to o.g atmospheres. 
The Triumph ice box potatoes gave a somewhat larger variation 
when filtered and unfiltered sap collections were tested, one reading 
amounting to 1.08 atmospheres greater pressure in the unfiltered 
specimen. 
The difference of pressure in the sap taken from a large and a 
small Burbank in the ice box ranged from 0.5 to 1.32 atmospheres, 
and in the case of sap obtained from a large and a small Triumph, 
kept in the ice box for 8 weeks, there were 1.69 atmospheres in 
favor of the larger specimen. 





Gio ot 


: 
ws 
~ 



ATMOS: Aes 




PRESSURE 
= 
a 


























eeeee i oe + 




“ae 
DAYS 

Fic. 3 
The third graph (fig. 3) represents the readings which have 
been taken in a study of the Dakota Red, which is a very large 
potato, and the Snowflake which is much smaller. This set of 
readings extended from October 31, 1912, to July 1, 1913. Again 
the rapid ascent of osmotic pressure in the potatoes kept in the ice 
box is clearly shown, whereas the osmotic pressure of those kept 
at room temperature declined. 
The rapid lift in the curves B and D in the room temperature 
potatoes is associated with the loss of water which left these spec 
mens and moved into young potatoes that were developed between 
