1857.] The Seed. 51 



a plant already formed, it is perfect in all its parts, although in a 

 rudimentary state. When the seed begins to germinate, this embryo 

 first lengthens its radicle, then what is called the caulicle, and after- 

 wards sends the plumule upward, in the form of the stem and leaves. 

 In most plants, the cotyledons are gradually raised to the surface by 

 the extension of the caulicle, after which they become gi*een and act 

 as leaves. The phenomena attending the germination of a seed are 

 most interesting. The external agents necessary to the production 

 of germination, are water, heat and air. When a seed is exposed to 

 these agents, it swells, bursts its envelopes, and the embryo contained 

 is wakened into life. Now what has taken place to effect this inter- 

 esting result. The water has penetrated the substance of the seed, 

 softened its coverings, causing the embryo to enlarge, produc- 

 ing changes in cellular matter, rendering it suitable for the food of 

 the young plant, and affording it, before it can take care of itself, 

 with the materials of its nutrition. It also carries with it the gase- 

 ous, or solid substances, which the young plant requires. The quan- 

 tity of wafeer must not be in excess, otherwise the germinative power 

 would be destroyed — we speak here of land plants. Water then per- 

 forms in germination, two important offices, it softens the coverings 

 of the embryo, and affords a solvent and vehicle to the substances 

 which form the aliment of the plant. 



Heat is no less important to this wonderful process of germination. 

 Germination can not take place at a temperature below zero, and at 

 that point vegetable life would be forever inactive. But the heat, 

 like the moisture, must not be in excess, if so, it will destroy the vi- 

 tal principle. Air, likewise, is both essential to germination, as well 

 as to the growth of plants. Were a seed totally withdrawn from con- 

 tact with air, it would forever remain in a quiescent state. And we 

 must remember, in this connection, that air is not a simple body, but 

 is formed of oxygen, and what is called azote or nitrogen; and though 

 not certainly known, yet it is probable, both are necessary to vegeta- 

 tion and healthful development. The action of air upon plants, at 

 the first period of their development, presents the same circumstan- 

 ces as in the respiration of animals. It is the oxygen of air that 

 gives the blood the qualities which fully develop the organs, and the 

 same oxygen imparts a healthy and vigorous development to the 

 plant. Here we learn how these various agents combine to quicken 

 into life the embryo plant, and with what harmony and order nature 

 performs her mysterious work, arresting the attention of the curious 

 beholder to wonder and admire. 



