VEGETABLE PHYSIOLOGY. 65 



When a seed is committed to the soil under the conditions 

 that have been just specified, it begins, for the most part, soon 

 after to inhale or imbibe air and moisture, and to expand and 

 augment in volume. This is uniformly the first symptom of 

 incipient germination, though not always an infallible symptom ; 

 because the seed may swell with moisture merely by being 

 soaked in water, though the vital principle should be totally 

 extinct. But the first infallible symptom of germination is to be 

 deduced from the prolongation of the radicle beyond the extent 

 to which it would attain merely in consequence of soaking. In 

 the latter case the augmentation of the radicle is limited by the 

 extent and capacity of its envelopes, or by the quantity of moisture 

 necessary to its saturation ; or by causes inducing incipient 

 putrefaction. But in the former case its augmentation is circum- 

 scribed by no such limits : for it not only assumes a swollen and 

 distended appearance in consequence of the absorption of 

 moisture ; but acquires an additional and progressive increase 

 in the actual assimilation of nutriment, bursting through its proper 

 integuments, and directing its extremity downwards into the soil. 



The next step in the process of germination is the evolution of 

 the cotyledon or cotyledons, unless the seed is altogether a 

 cotyledonous. 



The next step, in the case of seeds furnished with cotyledons, 

 is that of the extrication of the plumelet, or first real leaf, from 

 within or from between the cotyledon or cotyledons, and its 

 expansion in the open air. 



The last and concluding step is the developement of the 

 rudiments of a stem, if the species is furnished with a stem, and 

 the plant is complete. 



Such are the phenomena observable in the germination of 

 seed ; air and moisture are absorbed from the soil or atmosphere 

 by the hilum or envelopes. Their agency is immediately 

 exerted on the farina of the albumen or cotyledons ; and a food 

 is thus prepared for the nourishment of the tender embryo, to 

 wdiich it passes through the medium of the vessels of the 

 cotyledons, or, as they have been also denominated, the seminal 

 root. The radicle gives the first indications of life, expanding 

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