566 LECTURE LVIII. 



Vegetables derive their existence, by seeds, or otherwise, from a parent 

 stock, their parts are extended and evolved from within, and they imbibe 

 their nutriment by superficial absorption only. There is indeed in the 

 crystallization of minerals a slight resemblance to a reproduction or genera- 

 tion, when a small portion of the substance serves as a basis for the forma- 

 tion of subsequent crystals : but this portion becomes a constituent part of 

 the crystal, while it preserves its original form ; a seed, on the contrary, is 

 a substance naturally and completely detached from the plant, and con- 

 taining within itself the simplest rudiments of a new individual, which is 

 afterwards evolved and enlarged. Sometimes, however, vegetables are pro- 

 pagated by means of bulbs, or by spreading roots, by slips, or by ingrafted 

 scions, without a seed detached in the regular manner ; but in these cases 

 the new plant is much more identical with the old one, than when it is 

 raised from a seed, being as it were a continuation of the same existence. 

 Plants are nourished in great measure by means of their roots ; and some- 

 times, where they are without roots, their nutriment is probably absorbed 

 by all parts of their surface. 



Animals are distinguished from vegetables by the reception of their 

 food, for digestion and assimilation, into an internal cavity constituting a 

 stomach. The existence of a stomach, calculated for the digestion of food, 

 appears to be the best, if not the only criterion of an animal. Some vegeta- 

 bles, indeed, have a power of catching and detaining animals, by curling 

 up their leaves so as to cover them, as the drosera or sundew, and the 

 dionaea muscipula, or catchfly ; but this mechanism can scarcely be 

 intended for their immediate nutriment, at least the leaf can scarcely be 

 supposed to assume the character of a stomach. It is true that we imagine 

 all animals to have sensation, and all plants to be without it ; and if it were 

 possible to discriminate decisively between sensation and irritation, the dis- 

 tinction would supersede every other : but in many cases it is extremely 

 difficult to say where sensation is present, and where irritation only pro- 

 duces the same apparent effects. We cannot be sure that the hydra, or 

 fresh water polypus, or the trichurus sol, an animalcule described by 

 Dr. Shaw, suffers any sensation of pain when it is divided into two parts ; 

 at least the pain seems to agree remarkably well with its constitution, for 

 it lives and thrives with increased vigour, as two distinct animals. On the 

 other hand, many plants are easily stimulated to perform motions, which 

 have the appearance of muscular actions, influenced by sensation : the sen- 

 sitive plants close or depress their leaves, in consequence of agitation or of 

 electricity ; the stamina of the barberry and of the pellitory are thrown 

 into motion, when touched with a needle, and those of rue, and of the 

 grass of Parnassus, have at times alternate motions without any apparent 

 cause. A zoophyte is an animal absolutely fixed to one place ; and the 

 vallisneria is a vegetable possessed of a certain limited power of locomotion. 

 A plant chooses in preference to turn towards the light ; and it has been 

 known that an ash tree on a wall, when incapable of being any longer sup- 

 ported by the wall only, has concentrated all its force in the production of 

 one large root, descending to the ground. Some of these circumstances 

 may be explained without recurring to any thing like volition ; but, as 



