2l6 



the barked cherry trunk. We must imagine that all the tissue here shown 

 in the form of a callus covered with bark rests upon the old wood cylinder 

 from which the bark has been removed. 



Since reference to the anatomical processes, leading to the formation of 

 this new tissue on the exposed wood, is made in the chapter "Wounds" 

 (bark wounds), we will mention here only the fact that, if at any given time 

 the bark is removed from a tree, the newest cambium, thus exposed, begins 

 to grow again and covers the wounded surface with a parenchymatous tissue 

 layer. This parenchymatous covering is increased by the later appearance 

 of a constant meristematic layer. The inner surface of this layer forms 



Fig- 



Newly formed wood and bark body on the bark wound of 

 The bark shows a lenticel excrescence. (Orig.) 



cherry trunk. 



normal cambium, which gives rise to woody tissues toward the centre and 

 back towards the periphery. 



Figure 28 is a new structure several months old which, in the form of a 

 broad wrinkled callus, has grown on the cambium of an experimentally 

 barked sweet cherry trunk. The old wood of the barked trunk has been 

 omitted in the drawing; it would join on at hp. The cambial zone (c) 

 has sharply differentiated this tissue into wood and bark. The wood, where 

 it rests on the old trunk, has a parenchymatous structure {hp) ; which later 

 passes over into a vascular new wood {nh) forming libriform fibres. The 

 structure of the bark is at first irregular and corresponds to the formation 

 of wood which only gradually obtains its normal structure, for the hard 



