Manchester Memoirs, Vol. lix. (1915), -Afo. 3. 9 



lower aspect of the stock, which progressively exposes 

 new roots on the surface. The root-bearing surface 

 {Fig. I, b 1 ) thus exposed bounds the lower face of the lobes 

 and the lower portion of their sides. It also is in its 

 origin a split surface, but it will have to be considered 

 later whether it does not in a sense represent a portion of 

 the true outer surface of the plant. The splitting in the 

 root-bearing region is a necessary expression of the active 

 growth and differs from the passive splitting induced by 

 it in the leaf-bearing cortex. The older cortex, both 

 leaf-bearing and root-bearing, is thus divided into two 

 lobes. The tissue composing the distal older portions of 

 these perishes. The dead tissue is not actually shed, but 

 when it decays or is removed the end of the lobe is 

 bounded by a scar-surface {Fig 1, c). This is obviously 

 not a portion of the true outer surface of the plant. 



We thus distinguish as surfaces of the stock {Fig. 1) : 



a. The true external leaf-bearing surface. 



b. The split surface of the groove below and extend- 



ing up the sides of the stock. 

 b\ Split surface bearing roots. 

 b 2 . Split surface in leaf-bearing cortex. 



c. Scar surface at ends of lobes when dead tissue is 



removed. 

 The internal construction of the stock must be 

 thought of in the solid, either on the information supplied 

 by a complete series of transverse sections or by com- 

 bination of sectional views in different planes. This is 

 most easily done in the case of two-lobed plants, where 

 longitudinal sections can be definitely orientated in the 

 plane of the groove or the plane of the lobes, but there 

 is no difference in principle between the construction of 

 such plants and that of the three- or four-lobed stocks. 



