724 
CHEMICAL PROCESSES IN THE PLANT. 
The apparatus described in my Handbook of Experimental Physiology, p. 271, may 
be easily employed, with the necessary modifications, for the observation of the pro- 
duction of carbon dioxide and the elevation of temperature of germinating, seeds. The 
following experiment is also adapted for the demonstration of these points in a lecture. 
One-third of a glass cylinder of 2 litres capacity is filled with soaked peas or some 
other seeds or with flowers in the act of unfolding {e.g. small flower-heads of Com- 
positae, as Matricaria or Pyrethrum), and closed with a well-fitting glass stopper. If 
the vessel is opened carefully after several hours, the air contained will be found to 
extinguish a burning taper let down into it, as if it had been filled with carbon dioxide. 
In order to observe the development of heat also in small quantities of seeds and 
even in single flowers of larger size, I use various forms of the apparatus represented 
in Fig. 472. The flask / contains a strong solution of potash or soda / which absorbs the 
carbon dioxide set free from the plants. In the opening of the flask is placed a funnel r, 
containing a small filter-paper perforated with 
a needle. The funnel is filled with soaked 
seeds or with cut flower-buds in the act of 
opening; and a bell-glass g is now placed 
over it, through the tube of which a thermo- 
meter graduated to tenths of degrees is let in 
so that the bulb is surrounded on all sides by 
the plants. A loose plug of cotton-wool iv 
closes the tube. In order to compare the 
temperature, a similar apparatus is placed 
close beside, in which the seeds or flowers as 
the case may be are or are not replaced by 
pieces of moist paper or green leaves. It 
is convenient to place both apparatuses in a 
large glass case in order still more completely 
to shield them from slow changes of temper- 
ature in the air of the room. As the isolation 
is not complete, the access of fresh oxygen- 
ated air to the plants is not hindered, and the 
continuance of respiration is therefore not 
prevented; the arrangement is on the other 
hand sufficient to reduce to a minimum the 
loss of heat by radiation and evaporation. 
The thermometers of both apparatuses, pre- 
viously compared, must be frequently read 
off" in order to detect the variations of ievctr 
perature. If the bulbs are small enough, the 
elevation of temperature in the funnel may 
be observed even with single flowers. In order to reduce still further the amount of 
evaporation and radiation, it is convenient, before the bell-glass g is placed over, to 
cover the funnel with a perforated glass plate, the thermometer being inserted through 
its perforation. 
It is possible under favourable circumstances to observe by means of this contrivance 
a rise of temperature of i'5°C. with 100 or 200 peas, while the roots are developing; 
the anthers of a flower of the Gourd caused a rise of about 0*8° G. in a tolerably large 
thermometer with the bulb of which they were in contact on only one side. A single 
capitulum of Onopordon Acanthium produced an elevation of 072° C. ; the stamens of a 
single Bower of Nymphoea stellata one of about o*6° G. The temperature of a number of 
flower-buds of Anthemis chrysoleuca heaped round the thermometer rose as they unfolded 
about 1*6° G. 
It will be readily understood that flowers must not be used for these experiments as 
Fig. 472.- 
-Apparatus for observing the rise of temperature 
in flowers and germinating seeds. 
