RESPIRATION IN GERMINATION AND FLOWERING. 185 



sugar, which forms an appropriate food for it. Had Sugar been 

 deposited in the first instance, it would have probably undergone 

 fermentation, and would have thus lost its utility, before the 

 time came for its office to be performed ; but the deposition of 

 Starch, which can remain unchanged for almost any length of 

 time, and which can at any time be converted into sugar, secures 

 these objects in the most effectual manner. Starch differs but 

 little from sugar in chemical composition, except in containing 

 one additional proportion of carbon. When germination com- 

 mences, oxygen is absorbed by the seed, in the substance of 

 which it combines with the carbon that is to be set free from it; 

 and a large quantity of carbonic acid is then given forth again to 

 the air, whilst, in the same proportion, the starch is converted 

 into sugar. 



284. It is in this manner, that the nearly tasteless barley is 

 changed into sweet malt ; and the change in the air around, ex- 

 hibits to us the function of respiration in its least complex form. 

 Darkness favours it ; since, as will presently be shown, a change 

 of contrary character is favoured by light. It is an interesting 

 fact that, after many trials, germination has been found to take 

 place most readily in an atmosphere consisting of 1 part Oxygen, 

 and 3 parts Nitrogen ; which is nearly the proportion of these 

 ingredients, in the air we breathe. If the quantity of oxygen is 

 much increased, the seed loses its carbon too rapidly, and the 

 young plant is feeble ; and if the proportion is too small, carbon 

 is not lost in sufficient amount, and the young plant is scarcely 

 capable of being roused into life. 



285. The changes which take place in Flowering, are very 

 similar to those occurring in germination. At the bottom of the 

 flower is usually a fleshy expanded body, into which its different 

 parts are inserted ; this is called the disk or receptacle. Here, 

 too, there seems to be a sort of reservoir of starchy matter, for the 

 nourishment of the newly-produced germs ; which is converted, 

 as in the other case, into sugar. A part of this is probably ab- 

 sorbed into the interior ; but the superfluous portion flows off 

 in the form of honey. During the conversion of the starch into 

 sugar, a large quantity of carbonic acid is substituted for the 



