5206 OF PLANTS. 



that, in this class, two purposes are to be provided for (and 

 together,) fructification and support, the fruitage of the 

 plant, and the sustentation of its stalk, what means could 

 be used more effectual, or, as I have said, more mechanical, 

 than what this structure presents to our eyes? Why or 

 how, without a view to this double purpose, do two shoots, 

 of such different and appropriate forms, sprint from the 

 same joint, from contiguous points of the same stalk ? It 

 never happens thus in robust plants, or in trees. " We 

 see not," says Ray, ** so much as one tree, or shrub, or 

 herb, that hath a firm and strong stem, and that is able to 

 mount up and stand alone without assistance, furnished 

 with these tendrils.^* Make only so simple a comparison 

 as that between a pea and a bean. Why does the pea put 

 forth tendrils, the bean not ; but because the stalk of the 

 pea cannot support itself, the stalk of the bean can; we 

 may add also, as a circumstance not to be overlooked, that, 

 in the pea tribe, these clasps do not make their appearance, 

 till they are wanted ; till the plant has grown to a height 

 to stand in need of support. 



This word " support," suggests to us a reflection upon 

 the property of grasses, of corn, Eind canes. The hollow 



radicles, in whatever way they were protruded from the position of 

 the seeds, turned their points outwards from the circumference of the 

 wheel, and in their subsequent growth receded nearly at right angles 

 from its axis ; the germens (plumules) on the contrary, took the op- 

 posite direction, and in a few days their points all met in the centre 

 of the wheel. 



" When the centrifugal force was made merely to modify the force 

 of gravitation in the horizontal wheel, where the greatest velocity of 

 revolution was given, the radicles pointed downwards about ten de- 

 gi-ees below, and the germens (plumules) as many degrees above the 

 horizontal line of the wheel's motion ; and the deviation from the per- 

 pendicular was less in proportion as the motion was less rapid. 



" These facts afford a rational solution of this curious problem, re- 

 specting which, different plilosophers have given such different opin- 

 ions ; some referring it to the nature of the sap, as De la Hire, others, 

 as Darwin, to the living powers of the plant, and the stimulus of air 

 upon the leaves, and of moisture upon the roots. The effect is now 

 shown to be connected with mechanical causes ; and there seems no 

 other power in nature to which it can with propriety be referred but 

 gravity, which acts universally, and which must tend to dispose the 

 parts to take a uniform direction. 



" The direction of the radicles and germens (plumules) is such, that 

 both are supplied with food, and acted upon by those external agents 

 which are necessary for their development and growth. The roots 

 come in contact with the fluids in the ground ; the leaves are exposed 

 to light and air; and the same grand law which preserves the planets 

 Jn their orbits is thus essential to the functions of vegetable life." 

 JDavy's El dgr. Chem. ii. Ed. p, 32. Faxton, 



