349 



" Although the doctrine of a circulation (says ho), as maintained by 

 Mr. Knight, should he false, yet the account which he gives of tho 

 progress and agency of tlie sap, and proper juice, short of circulation, 

 may be true. The sum of the account is as follows : When the seed 

 is deposited in the ground, under proper conditions, moisture is absorbed 

 and modified by the cotyledons, and conducted directly to the radicle, 

 whicli is, by consequence, first developed. But the fluid, which has 

 been thus conducted to the radicle, mingling, no doubt, with the fluid 

 which is now also absorbed from the soil, ascends afterwards to the 

 plumelet, through the medium of the lubes of the alburnum. The 

 plumelet now expands, and gives the due preparation to the ascending 

 sap, returning it also, in its elaborated state, to the tubes of the bark ; 

 through which it again descends to the extremity of the root, not only 

 forming in its progress new bark, and new alburnum, but mixing also, as 

 Mr. Knight thinks, with the alburnum of the former year, where such 

 alburnum exists, and so completing' the circulation." — Physiolog. Bo- 

 tany, V. II. p. 244. See also, on the same subject, Kieser, Organ, des 

 Plantes, pp. 258, 259, &c. 



This note has been extended to an unusual length. But I conceived 

 that it would be interesting to the young planter, to have a brief account 

 of the principal theories, which have been formed of the Circulation of 

 the Sap, and the ultimate conclusion, to which late writers have come, 

 as it is one of the most obscure, though important processes, in the 

 whole of vegetable economy. 



Note III. Page 186. 



Although trees, as is said in the text, have no organs analogous to 

 the mouths of animals, for receiving their food, yet perhaps it may be 

 said, that animals sometimes take in their food like trees. Men, for 

 example, have been known to become so debilitated by age or disease, 

 that they could receive no food by the ordinary organ of the mouth. 

 The consequence has been that they were immersed in milk and veal- 

 broth baths, and fairly subsisted by means of absorption. Thus, every 

 one of their pores became like leaves, for the introsusception of food. 

 Some few years since, an instance occurred, in a noble duke of sporting 

 notoriety, who was so supported during the last months of his life. 



