BRIEFER ARTICLES. 
THE PHYSIOLOGICAL CONSTANTS OF PLANTS COMMONLY 
USED IN AMERICAN BOTANICAL LABORATORIES. I. 
THE series of papers of which this is the first will give the results of 
careful study undertaken to find which of our common plants are best 
adapted for the demonstration of each of the physiological phenomena of 
plant life. The work is being done in the Laboratory of Plant Physiology 
at Smith College with the advice of Professor W. F. GANonc. The litera- 
ture of the various subjects is of course being used; but citation will be 
omitted for the most part, because the work is all being done de novo, and 
for the sake of teachers rather than investigators. It is intended that the 
resultant data shall enable teachers of botany to select in each case the 
best plant for the particular experiment in hand, and to know quantita- 
tively the physiological behavior of each of the common kinds. Since most 
of the teaching of botany in this country is necessarily done in the winter, 
when out-of-door plants are not available, only greenhouse plants have pees 
considered; and of these for the most part only the more common kinds, 
which can be grown in any ordinary room. Exceptions have been made 
in a few cases where a less common plant has been found to be especially 
good. : 
I. CHLOROPHYLL SPECTRA. 
In order to compare the spectra of chlorophyll from differe 
is necessary to adopt some standard solution and some uniform metho 
examining the leaves. The optimum amount of leaf for giving 4 — 
solution, without filtering, from most leaves was found to be 25°" of the 
nt plants, it 
in 15°° of 95 per cent. ethyl alcohol, and accordingly I have pepe 
the standard solution. A larger proportion of leaf gives a clouded solu 
Icohol. Solu- 
which must either be filtered or be cleared by adding more 4 
tions may be made equally well with methyl or wood alcohol. ie 
The solutions were made as follows: A beaker was fitted with a ‘ 
in which three holes were made to allow two test tubes, holding the solutions, 
and a thermometer to be suspended in the beaker. The beaker = um 
with water and set on a tripod over a Bunsen burner. The ~~ C, 
temperature for extraction of the chlorophyll was found to be fl 
at which the water in the beaker was kept. A tin hood was set : 
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