114 GERMINATION. 



version of the crude material of green fruit into the palatable 

 ones of the ripe. For additional remarks on this topic, see 

 " vegetable products," pectose and its variations. 



Section 3. — Germination. 



203. By germination we understand the commencement ot 

 the vital action, which produces a development of the embryo 

 of the seed. The necessary conditions of germination are the 

 presence of ivater, heat, and oxygen gas. 



204. Germination cannot take place in the absence of any 

 one of these agents ; and in the absence of water, no effect is pro- 

 duced toward germination by the exposure to both of the other 

 agents. With it they act promptly. The water enters the seed 

 by the hilum, and passes to the perisperm by the chalaza, from 

 the perisperm to the embryo through its point of attachment. 

 This is the direct course of the fluid through appropriate vessels; 

 but in some cases, as in the Beans and Peas, it will penetrate 

 the testa and enter the embryo directly through its substance, 

 when the vessels of the hilum are obstructed, by being covered 

 with wax or other substances impermeable to water, but germi- 

 nation goes on much more tardily. 



205. Seeds will not germinate in a vacuum, nor in any gas 

 except oxygen ; nor in distilled or recently boiled water; but by 

 the presence of 0.3 of oxygen in any of these cases, germination 

 will commence. The action of the oxygen seems to be in com- 

 bining with the carbon of the seed, and forming carbonic acid ; 

 producing, as Raspail says, fermentation : a part of the acid is 

 thrown off, and a part no doubt elaborated by the increasing 

 embryo. It has been proved by Edwards and Collin, that the 

 oxygen which the plant uses does not all come from the air, but 

 that the embryo possesses the power of decomposing water, and 

 using the oxygen and hydrogen for different operations in de- 

 veloping the plant. It would seem, however, that a small 

 quantity of oxygen was necessary to produce a commencement 

 of the vital action, to give the first impulse to vitality. By nu- 

 merous experiments it has been proved, that the best proportion 

 of oxygen with other gases is as one to four, the ratio found in 

 nature in the constitution of the atmosphere. Seeds may be ex- 

 posed to other agents, and not germinate or lose their vitality. 



203. What do we understand by germination? What are the necessary 

 conditions? — 204. How does the water enter the seed? — 205. What gas is 

 necessary to germination ? What is the best proportion of oxygen ? May 

 »eeds retain their vitality and be exposed to other agents? 



