^ith reference to Gardening. 203 



which is called phytology : but it is unnecessary to enter into 

 the descriptions, or even notice all the terms, employed by 

 botanical physiologists, in their definitions of vegetables, for 

 this would greatly exceed the limits of a letter ; neither is it 

 necessary to mention those points on which all these writers 

 are agreed. I shall therefore confine myself to notice only 

 the more prominent particulars on which they disagree. 



The ancient writers considered every plant as an individual. 

 That the seed consisted of two principal parts or essences ; 

 namely, the plumula and rostellum. The first ascending and 

 becoming the visible part of the plant, and the other descending 

 and becoming the root. The faculty and use of the root being 

 to fix the plant in the ground, and to imbibe from thence the 

 proper nourishment and moisture for the support of the 

 head. That from this radical organ, and from supplies ab- 

 sorbed from the air, and light, and heat of the sun, the plant 

 received its crescive powers, became enlarged, and had its 

 parts, stem, leaves, flowers, and fruit, developed and ex- 

 panded to perfection. That, as the expansion proceeded, the 

 sap flowed in a constant stream upwards, ascending through 

 the tubular and cellular structure of the stem, branches, and 

 leaves, by the latter of which it was elaborated into the true 

 blood of the plant ; and when the fruit was perfected, and 

 fallen with the l^ives (if a deciduous tree), then, as the sum- 

 mer efforts of the plant were at an end, this vital fluid began 

 to ebb, and gently returned to the root again, there to remain 

 until called into action by the warmth of the following spring. 

 Hence, this direct and retrograde motion of the sap was, and 

 still is, called its circulation. To establish this fact, the fol- 

 lowing incidents are sufficient proofs : viz. If a cicatrix be 

 made across the bark and liber of a tree, the upper lip of the 

 wound heals by protrusion doiomvards, much faster than the 

 lower lip advances upwards : that a bud or graft, inserted 

 on an unsuitable stock, will, in time, be elongated downwards, 

 by the returning sap, into the ground, and furnish itself with 

 roots for its own future support : and that, if a bud or graft 

 of a variegated hollyj or jasmine, Scc^ be placed on an unva- 

 riegated stock, the suckers which may rise from such stock 

 will be variegated also. These, and many other instances 

 occurring in the practice of gardening, could not happen 

 without there was an actual circulation of the sap ; and this 

 showing, also, that the juice or blood of the plant is not only 

 the principal agent in the expansion and maturation of vege- 

 tation, but is also convertible into all the parts, qualities, and 

 forms of which plants are compounded. 



