

MOTION IN PLANTS. 349 



broadest sense. It must, however, be remembered, that the 

 inorganic crust of the Earth contains within it the same 

 elements that enter into the structure of animal and vegetable 

 organs. A physical cosmography would therefore be incom- 

 plete, if it were to omit a consideration of these forces, and 

 of the substances which enter into solid and fluid combina- 

 tions in organic tissues, under conditions which, from our 

 ignorance of their actual nature, we designate by the vague 

 term of vital forces, and group into various systems, in accord- 

 ance with more or less perfectly conceived analogies. The 

 natural tendency of the human mind, involuntarily prompts 

 us to follow the physical phenomena of the Earth, through all 

 their varied series, until we reach the final stage of the mor- 

 phological evolution of vegetable forms, and the self-deter- 

 mining powers of motion in animal organisms. And it is by 

 these links that the geography of organic beings of plants and 

 animals is connected with the delineation of the inorganic 

 phenomena of our terrestrial globe. 



Without entering on the difficult question of spontaneous 

 motion, or in other words, on the difference between veget- 

 able and animal life, we would remark, that if nature had 

 endowed us with microscopic powers of vision, and the inte- 

 guments of plants had been rendered perfectly transparent to 

 our eyes, the vegetable world would present a very different 

 aspect from the apparent immobility and repose in which it is 

 now manifested to our senses. The interior portion of the 

 cellular structure of their organs is incessantly animated by 

 the most varied currents either rotating, ascending and 

 descending, ramifying, and ever changing their direction, as 



rum et Historia oryctologica, quae non nisi pristinum orbis terra* 

 statum indicant, a Geognosia probe distinguendas." Humboldt, Flora, 

 Friburgensis subterranea, cui accedunt Aphorismi ex Physiologia 

 chemica Plantarum, 1793, pp. ix.-x. Respecting the "spontaneous 

 motion," which is referred to in a subsequent part of the text, see the 

 remarkable passage in Aristotle, De Ccelo, ii. 2, p. 284, Bekker, where 

 the distinction between animate and inanimate bodies is made to 

 depend on the internal or external position of the seat of the determin- 

 ing motion. " No movement," says the Stagirite, " proceeds from the 

 vegetable spirit, because plants are buried in a still sleep, from which 

 nothing can arouse them." (Aristotle, De Generat. Animal, v. i. p. 778, 

 Bekker) ; and again, "because plants have no desires which incite 

 them to spontaneous motion." (Arist., De Somno et Vigil cap. i. p. 455, 

 Bekker.) 



