10 Feb., 1917.] The Siimnitr Hud, d-c, of the Vine. 



99 



are absolutely united if the uuion is satisfactory. Now, all new tissues 

 of the vine, whether of wood or bark, have one common origin, and 

 this is the thin layer of cells known as cambium, the importance of 

 which is altogether out of proportion to its size or, to be more exact, 

 to its thickness. It is well to thoroughly understand where this cambium 

 layer is situated; this is shown in Fig. 12, which illustrates dia- 

 grammatically a section nirough a yearling cane of vine. The central 

 pith, perhaps rather more plentiful than is usual, is surrounded by a 

 ring of wood, the fibro-vascular bundles of which are separated by 

 medullary rays which extend from the pith to the bark. The cambium 

 layer is shown at c. Fig. 12, where it is represented by a line se.parat- 

 ins; the wood from the inner bark or phloem (also called bast tissue). 



Fig. 12. — Diagrammatic Section of a Yearling Vine Cane (after Guillon). 



r, caiiibiiim layer; j', woud (fibro-vascular bmidles separated by medullary 

 rays); ph. phlceni or inner bark, also termed bast layer; s, cork layer of bark; 

 h. outer bark; pc, perieyele (fibres of outer bark); pi, central pitli. 



The cambium layer consists of very active cells which, when the vine is 

 in full sap, are so soft and tender as to allow the bark to be readily 

 lifted from the wood. The almost gelatinous condition of this layer at 

 such a time exjilains the old, thougli erroneous, term of cambium fluid. 

 This layer is nevertheless composed of true tissue, the cells of which 

 multiply rapidly, producing, on the inner side new wood, and on the 

 outer side new bark. It will suffice for the practical grafter to realize 

 that it is only at the cambium layer that new tissues are formed ; this 

 layer therefore plays a preponderant ]iart in the formation of the union 

 between stock and scion. 



22 



