Ch. XVI.] GERMINATION. J01 



;liat in the process of germination, oxygen gas unites with the 

 sarbcn of the seed, and carries it off in the form of carbonic 

 acid. Air furnishes that important agent, oxygen, which is the 

 first moving principle of life. 



420. Carbon constitutes the greater part of the suostimce of 

 seed ; and this principle being in its nature opposed to purtre- 

 faction, prevent seeds from rotting, previous to their being sown. 

 Some seeds having abundance of carbon, are capable of being 

 preserved for ages : while others, in which this element exists 

 but in small proportions, require to be sown almost as soon as 

 ripe j and such as are still more deficient in carbon, lose their 

 vital principle before separating fir ;in the pericarp. 



421. Oxygen is important U- germination, on account of its 

 agency in removing the carbon which holds the living principle 

 of the seed in bondage. 



422. The absence of light is unfavourable-to the germina- 

 tion of seeds ; for light acts upon plants in such a manner as to 

 take away oxygen by the decomposition of carbonic acid gas r 

 and to deposite carbon ; now this is just the reverse of the pro- 

 cess required in germination, where the carbon must be throw/? 

 off and the oxygen in excess. 



423. A certain degree of heat is necessary to germination. 

 Seeds planted in winter, will remain in a torpid state ; but as 

 soon as the warmth of spring is felt, the embryo emerges into 

 tife. By increasing heat, seeds may be hastened in their vege- 

 tating process ; thus the same seed, which with a moderate de- 

 gree of heat would germinate in nine hours, may be brought to 

 this state in six hours, by an increase of temperature. Too great 

 heat destroys the vital principle ; thus corn which has been 

 roasted can never be made to vegetate. 



424. There is a great difference in plants as to their time oj 

 germinating ; some seeds begin to vegetate before they are se- 

 parated from the pericarp.* In the greater number of vegeta- 



* In the month of January, on observing the seeds of a very fine juicy 

 apple, which had been kept in a warm cellar, I saw that they were 

 swollen, and the outward coat had burst; examining one seed by re- 

 moving the tegument and separating the cotyledons, I saw by the help 

 of a microscope the embryo, as if in a germinating state ; the radicle 

 was like a little beak ; in the upper part or plume was plainly to be seen 

 the tuft of leaves and the stem. 



420. What constitutes the greater part of thf substance of the seed i 



421. Why is oxygen necessary to germination'? 



422. Is light favourable to vegetation 



423. Is heat necessary to vegetation 7 



424. What is said of the difference in plants with respect to the nm* 

 of genninati >n 7 



