58 BOTANICAL GAZETTE [JULY 
a cork borer slightly smaller than the porous cup. The cup is 
connected by glass and rubber tubing to a horizontal reservoir 
made of a flat-sided “‘specimen bottle.” The reservoir is supported 
at the side of the scale pan by a light wire bracket, attached to 
a flat cork upon which the 
7890nNMI123456789ONRI1 294 56TE a ee 
Light aluminum shell containing 
eo By the plant rests. The second 
10 oye ad Se tube at the upper end of the 
ae = porous cup affords an easy 
Saturation deficit method of filling the cup. 
After the water has been 
— 7 drawn up, this tube is 
is ehseaae a iA sealed with cement. The 
i\ air needed to replace the 
by a capillary tube. By 
extending this capillary 
water in the reservoir 
| tube beneath the water 
\\ level, the rate at which 
Vaporimeter 25 
enters through the stopper 
the water is removed may 
be approximated by the 
rate at which air bubbles 
enter. This may yield in- 
teresting results concerning 
the relative time of the 
absorption and _ transpira- 
» tion maxima. It is 0 
Fic. oo for part of the record of Course open to the same 
experiment 8 objections as the Reinke 
method of determining the 
relative rate of photosynthesis in submerged plants. 
The aluminum shells devised by GANONG! are very satisfactory 
for inclosing the pots. The 15 cm. shell seems to be the most satis- 
factory to use, regardless of the size of the pot, because of the larger 
volume of air inclosed. I have no quantitative data to prove 
Myriophy llum 
ro 
Pelargonium 
4 Bot. GAZETTE 41:212. 1906. 
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