248 BOTANY part i 



tion and the loss of heat by radiation are prevented and vigorously respiring plants 

 are selected. A quantity of germinating seeds (peas) shows under proper con- 

 ditions a rise in temperature of T G. The greatest spontaneous evolution of 

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

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

 even 20° C. Also in tlie large flower of the Victoria rcfjia temperature varia- 

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

 of an Aroid exhales, in one hour, up to 30 cubic centimetres CO2 ; 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. 



Specially high temperatures are obtained by cutting up living leaves in large 

 quantity and ensuring a sufficient supply of oxygen. Under these conditions 

 MOLISCH obtained a temperature of 60° C. The leaves naturally perished. 



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

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



In some fermentations, e.g. alcoholic fermentation, a considerable 

 quantity of heat is evolved. The heat of rotting manure is well known 

 and emj)loyed in the construction of hot-beds. 



In the fermentation of tobacco also a considerable rise in tempera- 

 ture takes place. This is still more marked when damp ha}' or cotton- 

 wool is piled up in large quantity and left undisturbed ; by the forma- 



Fi(i. 205. — Protonema oi Schhtostega osintiadHcen. Tb« lens-shaped cells concentrate the feeble 

 light available to the habitat of the plant upon the chloroplasts. (Cf. Fig. 20:j.) 



tion of easily inflammable gases, this may lead to the spontaneous 

 combustion of the material. JMiEHE 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 

 organi-sms perish owing to the temperature to which they have given 

 rise and the hay becomes sterile (^*'). 



Phosphorescence ('"'). — Under the same conditions as those of respiration a 

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

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

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

 Fungus Armillaria mcllea. As further examples of spontaneously luminous Fungi 



