324 HOW CROPS GROW. 



Of the elements that assume the gaseous condition, car- 

 bon does so to the greatest extent. It unites with atmos- 

 pheric oxygen (partly with the oxygen of the seed, ac- 

 cording to Oudemans) producing carbonic acid gas (CO Q .) 

 Hydrogen is likewise separated, partly in union with 

 oxygen, as water (H 2 O), but to some degree in the free 

 state. Free nitrogen appears in considerable amount, 

 (Schulz, Jour, fur Prakt. Chem., 87, p. 163,) while very 

 minute quantities of Hydrogen and of Nitrogen combine 

 to gaseous ammonia (NH 3 .) 



Heat developed in Germination. These chemical 

 changes, like all processes of oxidation, are accompanied 

 with the production of heat. The elevation of tempera- 

 ture may be imperceptible in the germination of a single 

 seed, but it nevertheless occurs, and is doubtless of much 

 importance in favoring the life of the young plant. The 

 heaps of sprouting grain seen in the malt-house warm so 

 rapidly and to such an extent, that much care is requisite 

 to regulate the process ; otherwise the malt is damaged by 

 over-heating. 



2. The Transfer of the Nutriment of the Seedling 



from the cotyledons or endosperm where it has undergone 

 solution, takes place through the medium of the water 

 which the seed absorbs so largely at first. This water 

 fills the cells of the seed, and, dissolving their contents, 

 carries them into the young plant as rapidly as they are 

 required. The path of their transfer lies through the 

 point where the embryo is attached to the cotyledons ; 

 thence they are distributed at first chiefly downwards into 

 the extending radicles, -after a little while both down- 

 wards and up wards toward the extremities of the seedling. 

 Sachs has observed that the carbohydrates (sugar and 

 dextrin) occupy the cellular tissue of the rind and pith, 

 which are penetrated by numerous air-passages ; while at 

 first the albuminoids chiefly diffuse themselves through 



