PROCESS OF GERMIXATIOX. 5 



fi-om the deep subsoil, and exposed to the atmosphere, 

 becomes covered Avith vegetation, arising from seeds 

 which, for their developement, requked free access of air. 

 Lowness of temperatm^e tends to annul or retard the 

 influence of the air upon the process of germination ; 

 whilst increase of temperature, with a proper supply of 

 moisture, accelerates the chemical changes in the seed. 

 No seed germinates below 32° Fahrenheit ; each ger- 

 minates at a definite temperature, and therefore in fixed 

 seasons of tlie year. The seeds of Vicia faba, Phaseolus 

 vulgaris^ and the poppy, lose the power of germinating 

 when dried at 95° Fahrenheit; while barley, maize, 

 lentil, hemp, and lettuce seed retain the power at that 

 heat ; but wheat, rye, vetch, and cabbage seed will 

 germinate even at 158° Fahrenheit. 



During germination, oxygen is taken up from the air 

 around the seed, and an equal volume of carbonic acid is 

 evolved. 



If seeds are set to germinate in glasses, with a slip of 

 litmus paper fastened on the inside, the paper is red- 

 dened, often after a very short time, owing to the dis- 

 engagement of acetic acid : the most abundant and rapid 

 evolution of free acid was found to take place in the 

 germination of cruciferous plants, cabbage, and rape- 

 seed (Becquerel, Edwards). Certain it is that the fluid 

 contents of the cells of the roots, as well as the sap of 

 most plants, have an acid reaction, from the presence of a 

 non-volatile acid ; the sap of the young spring shoots of 

 the vine yields, upon evaporation, an abundant crystallisa- 

 tion of bitartrate of potash. 



By the experiments of Decandolle and Macau-e, wliich 

 have not yet been controverted, it was shown that vigorous 

 plants of ChondrUla muralis and Phaseolu.^ vuhjaris^hivh 

 had been taken from the ground, with their roots, and 



