244 ON THE SEED. 



Mrs. B. To a certain degree : seeds cannot germinate 

 during a frost, for the water must be in a liquid state : 

 about ten degrees of Reaumur, or fifty-five of Fahrenheit, 

 is the temperature most favorable to the germination of 

 plants in these climates. It is, moreover, requisite that 

 the soil should be sufficiently permeable for the slender 

 plumula, and the tender roots, when first shooting from 

 the seed, to penetrate it ; and, on the other hand, it must 

 be sufficiently compact to support the roots and stem 

 when full grown. The looser the soil is, the deeper the 

 seed should be sown, in order to afford more support. 



Emily. And in very loose soils the air has freer access, 

 so that there is no danger of depriving the seed of oxygen 

 by sowing it deep. Large seeds, I suppose, require to be 

 sown deeper than small ones? 



Mrs. B. Yes ; but the largest should not be buried 

 more than six inches in the ground, in order that the air 

 may have access to them. Small seeds require to be 

 merely covered with earth, in order to prevent the wind 

 from scatering them, and to shelter them, in some meas- 

 ure, from the light. 



Caroline. Is light, then, injurious to germination ? 



Mrs. B. The function of light, you may recollect, is 

 to subtract oxygen from the plant, and occasion a depo- 

 sition of carbon. Now, in germination, it is just the re- 

 verse which is to be effected. 



When the seed, by absorption, has accumulated a suffi- 

 cient quantity of moisture, it swells, bursts, the radicle 

 shoots downwards, and the plumula rises in the opposite 

 direction : the one becomes a root, the other a stem ; 

 and the almond of the seed is transformed into cotyledons. 

 If any of these parts are destroyed, the plant is no doubt 

 injured, but nature will restore them by fresh shoots. The 

 neck, or vital spot which forms the junction between the 

 stem and the root, being the only part, the destruction of 

 which proves fatal to the plant. 



Emily. Is it known why the stem always rises, and the 

 root descends. 



1332. What degree of heat is needed for germination! 1333. 

 What should be the consistency of the soil that the seeds germinate well! 

 1334. How deep should seeds be buried! 1335. What is the func- 

 tion of light! 1336. What takes place when the seed has acquired a 

 sufficient degree of moisture! 1337. What part must be destroyed to 

 prove fatal to the plant! 



