ON GROWTH AND EXTENSION IN THE VEGI/fABLE KINGDOM. 45 



stem. It is a curious circumstance, but not a rare one. that one 

 of the two grafted branches remained so much behind the other 

 in growth : so we iind on one side of a tree stronger branches than 

 on the other, which Du Hamel had already attributed to tlie 

 stronger and better-fed roots of the same side, and which can be 

 easily accounted for by the vessels ascending in a direct line, and 

 being but little branched. 



I have before me a branch of Fraxinus excelsior, five years 

 old, according to the rings, and eight lines in diameter. It had 

 been budded with a bud of Fraxinus atrovirens, which liad grown 

 into a branch of six lines in diameter, having also five annual 

 rings. Cut longitudinally it appealed as follows : the transition 

 from the stock to the budded branch was here also uninterrupted 

 through the outer layers of wood, but a brown line marks the 

 separation between the summit of the stock and the budded 

 branch. In the centre of this branch is a pith of four lines in 

 thickness, which terminates below towards the stock in a point. 

 The tliin layers of wood on the under side of the pith are curved 

 in an undulating manner towards the stock, the layers of the 

 upper side are curved upwards ; both originate in the portions 

 of bark which had served to fix the bud on to the stock, and which 

 as usual had borne a small portion of wood on the under side. 

 The interval between the layers had been filled up by a dense 

 mass of wood, in whicli can still be traced a brown line of loose 

 cellular tissue, showing probably the spot where the inner side of 

 the bud was fixed. Upon the whole, the circumstances appeared 

 the same in this instance as in that of the grafting. 



It is then in the outer layers of wood that the vital energies of 

 our trees reside ; in them the sap rises in spring ; and by their 

 means the increase and overgrowth in the interior of the trunk 

 is effected. 



It had appeared to me advisable to examine the growth of 

 grafts in succulent plants, and for that purpose grafted cactese 

 appeared peculiarly suitable. In several stems, of many years' 

 growth, I could find no internal distinction between the stock 

 and the grafted branch, till I received astern, of recent growth, 

 of Epiphyllum Altensteini, which had been cleft-grafted on a 

 stock of the same species.* In a portion of a transverse section 

 of the stem taken at the point where the graft had grown on, 

 we see the radiating woody fibres separated by broad medullary 

 rays, and the pith itself which occupies tlie greater portion of 

 the stem, and in tiie woody fibres are seen the large openings of 

 the descending spiral vessels. At the spot where the graft has 



* Mr. Reinecke, gardener to Mr. Decker, court-printer, a zealous pro- 

 moter of horticulture, had kindly grafted it for this purpose. 



