204 Vegetable Physiology^ mth reference to Gardeniftg. 



This is the system handed down to us by the fathers of 

 phytological research, and which continues to be espoused 

 by the first authorities of the present enlightened age. 



But within these last thirty or forty years another hypo- 

 thesis has been presented to public notice, I believe by the 

 late Dr. Darwin ; and which only requires to be placed by 

 description alongside of the foregoing, in order that the 

 attention of your young readers may be drawn to a study and 

 consideration of the question ; as haply, by experiment, they 

 may be able to come to such rational conclusion as will be, at 

 least, satisfactory to their own minds. 



Dr. Darwin considers a tree not as an individual, but as a 

 vegetable polypus. The trunk, or stem, is a common recep- 

 tacle, which has been formed by a bud, and is the supporting 

 foundation on which are borne all the numerous buds which 

 form the various branches, shoots, leaves, flowers, and fruit, 

 of the head. Each single bud is an individual perfect plant, 

 comprising all the essentials appertaining thereunto as such ; 

 it furnishes, and is furnished with, a radicle or radicles of its 

 own, which descend to the ground, and form, on the passage 

 thither, that part of the stem called the liber, or inner bark ; 

 and should these radicles be obstructed by a bough, they 

 wind their way on one or other side of it ; and, if arrested 

 by a cicatrix or wound, they endeavour to pass over rather 

 thian trend round, thus producing those descending processes 

 or protrusions above alluded to; which when they have reached 

 the ground, become additional roots. These radicles are the 

 roots which so readily issue from cuttings, and so soon form 

 the junction with the stock, in the practice of budding or 

 grafting. 



This hypothesis also assumes, that the pith maintains its 

 place along not only the principal stem, but is ramified as are 

 the branches. The wood or perfect timber which surrounds 

 it, is the ligneous remains of the radicles of former or extinct 

 buds. The alburnum (or what carpenters call the sap of 

 timber) is composed of the radicles of buds of former years, 

 not yet divested of their tubular structure, being kept dis- 

 tended by the sap in its state of elaboration, the inner surface 

 of which is annually attached to, and transformed into, tim- 

 ber, in concentric rings ; and the exterior surface receives at " 

 the same time a layer from the liber, formed of radicles of 

 still more recent formation. The liber, or inner bark, is the 

 most recently descending radicles of the living buds; an outer 

 portion of which is annually indurated, and becomes an 

 addition to the outer covering, or excrementitious bark of the 

 tree. The structure of this ligneous and fibrous formajion 



