646 CHEMICAL PROCESSES IN THE PLANT. 



considerable elevation of temperature of grains of barley in the manufacture of malt ; 

 and this elevation can also be proved in the case of other germinating seeds, or 

 growing bulbs and tubers. The proof is more difficult in plants with green leaves. 



In some flowers and inflorescences the production of carbon dioxide which 

 accompanies the inhalation of oxygen is very energetic, the radiation of the heat 

 produced being at the same time diminished by the small superficial extent of the 

 organ and by protecting envelopes ; and in such cases a very considerable elevation 

 of temperature of the masses of tissue has been observed. The best illustration of 

 this is the spadix of Aroidese at the time of fertilisation, where (especially in warm 

 air) an excess of temperature of from 4° to 5° or even of 10° C. or more has been 

 detected. Less considerable elevations of temperature have also been observed in 

 the separate flowers of Cucurbita, Bignonia radicmts, Victoria regia, &c. 



In the few cases in which up to the present time the development of light or 

 Phosphorescence has been observed in living plants, this phenomenon is also dependent 

 on the respiration of oxygen. In Agaricus olearius (of Provence) this has been 

 definitely proved by Fabre. This Fungus emits light only so long as it is alive, and 

 ceases to do so at once when it is deprived of oxygen ; the respiration is in this case 

 also very copious. Besides this Fungus, Agaricus igneus (of Amboyna), A. nocii- 

 lucens (of Manilla), A. Gardneri (of Brazil), and the Rhizomorphs are known to 

 emit light spontaneously ; the statements with respect to the light emitted from 

 various flowers are of extremely doubtful value ■. 



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 w^ith 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. 443. 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 thermometer graduated to tenths of degrees 

 is let in so that the bulb is surrounded on all sides by the plants. A loose pad of cotton- 

 wool <w 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 ap- 

 paratuses in a large glass case in order still more completely to shield them from slow 

 changes of temperature in the air of the room. If the isolation is not complete, the 

 access of fresh oxygenated 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 thermo- 



1 [For a collection of recorded instances of phosphorescence in plants see Hardwicke's Science 

 Gossip, 1871, p. 121. — Ed.] 



