256 HARMONIES OF VKGETATIO.1. 



3. Germination is accomplished by different circum- 

 stances, which are more or less necessary to excite the 

 vital principle of the seed. 



Although the earth is the natural bed for seeds, it is not absolutely 

 necessary. Various parasilical plants vegetate vrry well in the 

 chinks of the bark of other vegetables. Some seeds vegetate upon 

 the most barren rocks. But what is most to our purpose, the seeds 

 of many plants vegetate in water, and continue, during the whole 

 course of their lives, very completely detached from the earth. 



4. When a seed is placed in the soil, or in circum- 

 stances favourable to vegetation, the vital principle is 

 immediately stimulated into action, producing a variety 

 of combinations, and effecting a gradual change in the 

 parts of the plant. 



After the seed has been deposited in the soil, it begins, for the 

 most part, very soon to imbibe air and moisture, and increase in 

 size. The next step is the evolntion of the radicle; the cotyledons 

 begin to get soft and expand, and put on the appearance of seminal 

 leaves; the plumelet then becomes extricated and rises to expand in 

 the air, as the real leaf. The last and concluding step is the develope- 

 ment of the rudiments of a stem, provided the plant is furnished 

 with astern. 



5. There are several conditions, which are in a mea- 

 snre essentially necessary to germination. These are, 

 the maturity of the seed, the exclusion of light, a proper 

 degree of heat, and the access of moisture and air. 



6. Unripe seeds seldom germinate, because their 

 parts are not prepared to form the chemical combi- 

 nations on which germination depends. 



Although there are some instances in which the teed will germi- 



