732 



PART IV. — THE PHYSIOLOGY OF PLANTS. 



nexion with transpiration. It is however easy, under appropriate 

 conditions, to demonstrate the evolution of heat. If a quantity of 

 seeds be made to germinate in a heap, they will be found to be 

 distinctly warm (Fig. 476). This happens on a large scale in the 

 process of malting barle3\ When a large 

 quantity of barley- grains are germinat- 

 ing on a malting-floor, they become quite 

 hot: they have, in fact, to be continually 

 turned to prevent overheating. The 

 conditions are here most favourable ': 

 for the catabolic processes are extremely 

 active in germinating seeds, and there 

 is but little loss of heat by radiation 

 and transpiration. Similar observations 

 may be made with opening flower-buds, 

 the opening of the bud being also a 

 period of great catabolic activity. In 

 some cases, as in the Araceae, where the 

 inflorescence consists of a great number 

 of flowers which open simultaneously, 

 and which are protected by a large leaf, 

 the spathe, a rise of temperature as 

 much as 18° C. has been observed. 



The few plants in which an evolution 

 of energy in the form of light has been 

 clearly established are all Fungi. It is 

 commonly termed phosphorescence. The 

 so-called phosphorescence of decaying 

 wood is due to the presence of the my- 

 celium of Agaricus melleus, and that of 

 putrifying meat and vegetables to Schi- 

 /omycetes of the nature of Micrococci. 

 Various other species of Agaricus have 

 been found to be luminous. 



Movement of some kind is manifested 

 by all plants. All plants exhibit that 

 slow movement which is termed growth : 

 in many, there is a more or less well- 

 marked movement of the protoplasm in 

 the cell or cells of which the plant-body 

 consists, which is known as cyclosis, cir- 



FiG. 476.— Apparatus for de- 

 tecting the rise of temperature 

 in small opening flowers or ger- 

 minating seeds. The seeds are 

 heaped as closely as po-sible in 

 the funnel r which is inserted 

 into the mouth of a bottle con- 

 taining a solution of caustic 

 potash. This absoi'bs the car- 

 bon dioxide produced by respi- 

 ration. The whole is enclosed 

 in a glass vessel, and a delicate 

 thermometer is inserted through 

 the cotton wool which closes 

 the mouth. The bulb of the 

 thermometer is plunged in 

 among the seeds. The tempera- 

 ture in this apparatus will be 

 higher than in another arranged 

 in the same way for comparison, 

 Snd in which the flowers or 

 seeds are replaced by scraps of 

 paper, etc. 



