68 LESSONS IN CHEMISTRY. 



the grain into the sugar of the wort, is produced. By means 

 of this substance, which is discovered just at the point where 

 the vessels extend from the seed to the sprout, the starch is 

 dissolved, and, accompanied by the transformed gluten, made 

 to contribute under the form of dextrin and sugar to the 

 production of cellular fibre, of which the earliest formed parts 

 of the young vegetable are composed. 



94. For the healthy germination of the seed, as the first 

 stage of vegetable growth is usually termed, there are certain 

 essential conditions. 



Moisture. Water is necessary in all the curious chemical 

 changes by which the transformations lately described are 

 effected. It is well known to the farmer that by steeping 

 hard seeds in water for some time previous to sowing he will 

 facilitate their growth. A perfectly dry seed will remain 

 for years without exhibiting any sign of life, but if placed in 

 a damp situation its inactivity disappears and it begins to 

 germinate. An excess of water in the soil is, however, 

 injurious to healthy vegetation, though some seeds sprout 

 and flourish in situations where most of our cultivated grains 

 would rot or produce an inferior crop. 



95. Air. Without a proper supply of air no seed can ger- 

 mmate. When a piece of charcoal is burned in a vessel of 

 oxygen gas, it is found that the bulk of the gas in the vessel 

 is not diminished, but that its properties have been changed, 

 a quantity of carbonic acid gas is formed equal in volume 

 to the oxygen which has disappeared. A precisely similar 

 change is effected by causing seeds to germinate in a receiver 

 containing common air or pure oxygen. In both cases, 

 oxygen gas disappears, and nearly an equal bulk of carbonic 

 acid is produced at the expense of the carbonaceous matters 

 (starch, &c.) of the seed.* Buried too deep in the soil where 

 the oxygen of the atmosphere cannot reach them, seeds 

 remain for centuries unchanged. 



96. Heat. A proper temperature is no less necessary for 

 the development of the seed than air and moisture. Below 

 the temperature at which water freezes, germination does not 

 take place. 



In Europe and North America, the corn crops germinate 

 at temperatures from 43° to 48° (Boussingault), and merely 



* Some acetic acid (78) is also produced in germination; thus, ger- 

 minating seeds placed upon blue test paper are found to colour it red. 



