DIV. ii PHYSIOLOGY 277 



conditions a rise in temperature of 2 C. The greatest spontaneous evolution of 

 heat manifested by plants has been observed in the inflorescences of the Araceae, 

 in which the temperature was increased by energetic respiration 10, 15, and 

 even 20 C. Also in the large flower of the Victoria regia temperature varia- 

 tions of 15 C. have been shown to be due to respiration. One gramme of the spadix 

 of an Aroid exhales, in one hour, up to 30 cubic centimetres C0 2 ; and half of 

 the dry substance (all the reserve sugar and starch) may be consumed in a few 

 hours as the result of such vigorous respiration. These high temperatures in 

 flowers and inflorescences attract insects that are of use in pollination. Specially 

 high temperatures are obtained by cutting up living leaves in large quantity and 

 ensuring a sufficient supply of oxygen. Under these conditions the temperature 

 to 40-50 C., and the leaves perish. After their death a further rise of 

 temperature is due to the action of micro-organisms. 



In the healing of wounds in plants, respiration and also the production of heat 

 are markedly increased ; the contrary ^s seen in conditions of starvation. 



In the fermentation of tobacco also a considerable rise in temperature takes 

 place. This is still more marked when damp hay or cotton wool is piled up in 

 large quantity and left undisturbed ; by the formation of easily inflammable gases, 

 this may lead to the spontaneous combustion of the material. MIEHE has most 

 recently investigated the spontaneous heating of hay. First by the respiratory 

 activity of Bacillus coli the temperature is raised to 40 C. ; then a number of 

 thermophilous Moulds and Bacteria become established, among which Bacillus 

 calfador raises the temperature to 70 C. Ultimately all the organisms perish 

 owing to the temperature to which they have given rise and the hay becomes 

 sterile. 



Phosphorescence ( 51 ). Under the same conditions as those of respiration a 

 limited number of plants, particularly Fungi and Bacteria, emit a phosphorescent 

 light. The best-known phosphorescent plants are certain forms of Bacteria which 

 occur in the sea, and the mycelium, formerly described as "Rhizomorpha," of the 

 Fungus Armillaria mellea. Harmless phosphorescent Bacteria (Microspira photo- 

 ycna, Pseudomonas lucifera] occur on phosphorescent fish or meat. According 

 to MDLISCH Bacterium phosphoreum (Micrococcus phosphoreus] usually occurs on 

 meat which has been moistened with a 3 per cent solution of common salt and 

 kept at a low temperature. The most important plants, in addition to many 

 animals, taking part in the phosphorescence seen in the sea are Pyrocystis noctiluca, 

 belonging to the Gymnodiniaceae and certain Peridineae. 



This phosphorescence at once disappears in an atmosphere devoid of oxygen, 

 only to reappear on the admission of free oxygen. On this account the phos- 

 phorescent Bacteria, according to BEYEUINCK and MOLISCH, afford a delicate test 

 for the activity of assimilation. All the circumstances which facilitate respiration 

 intensify phosphorescence ; the converse of this is also true. According to the 

 results of investigations concerning the phosphorescence of animals, from which 

 that of plants does not probably differ in principle, the phosphorescence is not 

 directly dependent upon the respiratory processes. Xo use is known for the 

 phenomenon of phosphorescence. 



