370 The Botanical Gazette. [September, : 
descent of the mercury in the tubes showed the rapidity of 
the passage of the gas. Gas passed through rhizomes very 
rapidly for the first hour, though becoming slower towards — 
the end of the -hour, and finally, as the rhizomes became 
saturated with the gas, becoming so slow as to takesome — 
times a day for the mercury in the tube to come to the level 
of that outside. The gas passed more rapidly through short 
than long lengths of rhizomes. 
2. To determine passage of gas through sections of epider- 
mis under pressure, sections of epidermis were fastened on 
the end of a glass tube, which was then filled with mercury 
and placed in a vertical position in a vessel of mercury. The 
mercury remained at its original height for days, though the 
sections would become concave from the pressure on them. 
3. To determine amount of diffusion of gases without pres- 
sure through living plant membranes and dead plant and 
animal membranes, sections of hog’s bladder and living and 
dead epidermis were fastened on tubes as before, the tubes 
being filled with water instead of mercury, the water then be- 
ing displaced by the gas. The sections permitted consider 
able diffusion to take place, though the greater amount Was 
attained by the living plant membrane. 
4. To determine rate and amount o tu 
through both epidermis and internal air cavities, 
rhizomes were fastened air-tight into tubes, rahe 
rhizomes extending into the tube being sealed. The 
were then filled with gas as before, carbon * 
and ammonia being feed. The ammonia killed the Paty ie 
so that no comparison between it and the other erik ae 
be made. The carbon dioxide showed greater pe: ier . 
amount of diffusion, and was uniform in diffusing, W ee 
hydrogen was subject to fluctuations, the mercury ate gases 
sometimes dropping to the level of that outside. . 
diffused more rapidly when the tempera i 
high temperature very probably causing the gas * a} plant 
ficient pressure to hinder diffusion. The 1 ree pndet 
was the factor of greatest importance, 45 like are amount 
similar conditions showed variations in the rate: ane 
of diffusion. 
chigan 
BEAL, Ws. J.: The sugar maples of Central Mit : 
Descriptions of A. barbatum and the var. nigrum a ae 
It was shown that A. saccharum barbatum ee 
