a 
DRIEPER A REGLE s 
NEW NORMAL APPLIANCES FOR USE IN PLANT PHYSI- 
OLOGY III 
(WITH TWO FIGURES) 
In the two preceding articles I described several pieces of apparatus 
newly devised for educational work in plant physiology and explained the 
objects I have in view in their development. In brief I aim to provide for 
each of the principal physiological processes such apparatus as will be 
accurate in results, convenient in manipulation, and obtainable by pur- 
chase from a supply company. The company to which the manufacture 
has been delegated is the Bausch & Lomb Optical Co., of Rochester, N. Y. 
In the earlier articles I named the appliances ‘‘precision-appliances,” 
which some, though not all of them are; they are, however, more properly 
normal appliances, which I shall henceforth call them. 
VI. PHOTOSYNTHOMETER. 
No fact in all the physiology of plants is more important, and hence 
more imperatively demands complete demonstration in botanical educa- 
tion, than the absorption of carbon dioxid by green plants in light, with the 
equivolumetric release of oxygen. There are simple ways of demonstrating 
the process in part, and somewhat complicated ways of demonstrating it 
completely; but hitherto there has been no simple method of demonstrating 
the entire process in one operation. This is effected, however, by the new 
photosynthometer described below, and illustrated in the accompanying 
fig-1. tis called by this name for the reason that it permits photosynthesis 
(the quantity of the photosynthate being a function of the quantity of the 
gases absorbed and released) to be measured as well as demonstrated. 
The instrument consists essentially of a pear-shaped plant-chamber set 
in a firm iron base, a graduated measuring tube with a small stop-cock at the 
upper end, and a connecting stopper furnished with a stop-cock of con- 
siderable bore. The total capacity of the apparatus when closed is exactly 
102°, of which the 2° is for a shoot and 100° for the gases concerned. The 
proper amount of shoot is provided by selecting a small-leaved plant and 
pushing a branch down into a measuring-glass until it displaces exactly 2°¢ 
* Continued from Bot. GAZETTE 39: 152. February 1905. 
209 | [Botanical Gazette, vol. 41 
