196 ZOOLOGICAL PHILOSOPHY 



or depression of stamens or peduncles or to the twining of climbing 

 stems and tendrils, finally, those constituting what is called sleeping 

 and waking in plants ; none of these movements are ever sudden ; 

 they are carried out so slowly as to be altogether imperceptible ; 

 and they are only known by their finished results. 



Animals, on the contrary, possess the faculty of performing very 

 obvious sudden movements, by means of some of their external parts, 

 and of repeating them several times in succession with or without 

 variation. 



Plants, especially those which live partly in the air, grow in a remark- 

 able manner in two opposite directions, in such a way as to exhibit 

 an ascending vegetation and a descending vegetation. These two kinds 

 of vegetation start from a common point which I have elsewhere ^ 

 named the vital knot, because in this point life is specially concentrated 

 when the plant loses its structures, and because the plant only really 

 dies when life ceases to exist in this part. The organisation of this 

 vital knot, otherwise known as the root-collar, is altogether pecuUar ; 

 from the vital knot the ascending vegetation produces the stem, 

 branches and all the parts of the plant that are in the air ; and from 

 the same point the descending vegetation gives birth to roots which 

 are buried in the soil or in water. Finally, in germination, which 

 brings the seeds into hfe, the early development of the young plant 

 requires ready prepared juices, which the plant cannot yet draw from 

 the soil or from the air ; these juices then appear to be furnished by 

 the cotyledons, which are always attached to the vital knot ; they 

 suffice for starting the ascending vegetation of the plumule and the 

 descending vegetation of the radicle. 



Nothing of the kind is observed in animals. Their development 

 is not limited to two special directions only, but takes place on all 

 sides and in all directions, according to their requirements ; finally, 

 their hfe is never concentrated in an isolated point but is spread through- 

 out the essential special organs, if there are any. In animals in which 

 there are no essential special organs, life is not concentrated in any 

 one part ; for when we divide their bodies hfe is preserved in each 

 separate part. 



Plants in general rise perpendicularly, not to the plane of the earth 

 on all occasions, but to that of the horizon ; so that according as they 

 grow they shoot upwards towards the sky like a sheaf of rockets in a 

 firework display. Although the twigs and branches which form their 

 tops do not follow the direction of the stem, they always form an 

 acute angle with the stem at their point of insertion. It appears 

 that the stimulating force of the vital movements in these bodies is 

 * Histoire Naturelle des Végétaux, édition de Déterville, vol. i., p. 225. 



