SECT. VIII. DESCENT OF PROPER JUICE. 1 9 



producing none. Hence he inferred that the bark 

 cannot be the channel of the descent of the sap 

 or proper juice, since the plant still lived in spite 

 even of the abstraction of several circular portions. 

 But if some plants are so very tenacious of life as to 

 survive even the violent operation of girdling, it will 

 not appear surprising if some plants should survive 

 also the gentler operation of a partial barking. For 

 in this case the proper juice may find a partial and 

 temporary channel even in the alburnum where it is 

 naturally of a very loose texture, and not too much in- 

 durated by exposure to air; and as the sap ascends, 

 at any rate by the alburnum, there is no difficulty in 

 accounting for the developement of the buds in the 

 above experiment. For wherever a bud is formed the 

 ascending juice will find its way to it, from which the 

 elaborated sap or proper juice will again descend 

 by the bark, its natural channel, at least till it meets 

 with some interruption ; where it will form tumors 

 as in the above case. And if no tumors were formed 

 on the lower lips of the rings without buds, it is 

 because there was no particular determination of sap 

 towards such rings on the very account of their want 

 of buds, and consequently no room for the process 

 of elaboration and return of proper juice. This was 

 accordingly Du Hamel's reply, and subsequent ex- 

 periment has shown it to be correct ; for the experi- 

 ments of Mr. Knight on this subject are, if possible, According 

 more convincing than even those of Du Hamel. toKm s ht - 

 From the trunks of a number of young Crab-trees 



