842 



An older example from Duhamel^ should be mentioned in this connec- 

 tion. Almonds grafted on plums and, conversely, plums on almonds, at 

 first grow very well but usually retrogress after one or several years. The 

 almond has a much more luxuriant habit of growth, sprouts earlier in the 

 year and, as scion, forms a strong roll at the place of grafting. It is 

 probable, therefore, that such a scion, requiring more water earlier and 

 constantly, will thrive on a less luxuriant stock as long as this is able to 

 satisfy the young twigs from its reserve store in the trunk. If the grafted 

 branch becomes several years old, its needs become greater and, if it cannot 

 accommodate itself to the stock, as frequently occurs (dwarf trees of seed 

 fruits), it gradually degenerates from a lack of nutriment. The results vary 

 greatly, according to soil, amount of water and variety. Conversely, a 

 stock which blossoms too early and grows too luxuriantly will supply more 

 to a scion, requiring a lesser amount, than this can take up. The super- 

 fluous material from the stock is quickly worked over into new structures. 

 If many groups of buds are present, this excess manifests itself in the pro- 

 duction of long shoots. If, however, as in grafting, most of the lateral 

 buds, or eyes, are suppressed, the material remains at the disposal of the 

 thickening ring of the trunk. Thus, instead of prosenchymatous elements, 

 aggregations of wood parenchyma are formed, which, in the Amygdalaceae, 

 easily become gum centres as I also have observed. Among the older 

 observers, Duhamel reports that almond stock, grafted with plum scions, 

 will die from gummosis at the place of grafting. 



Experience has also taught, in the very general practice of grafting 

 pears on quince or apples on Paradise stock, that death sets in the more 

 quickly for rapid growing scions, the drier the soil and the fewer the roots 

 which the stock has developed in it. The scions fail much the more rapidly. 

 Duhamel also cites cases when, under such disproportionate need of water 

 in scion and stock, even simple transplanting has led to death through failure 

 of union (almonds on plum stock), while the little trees of the same series, 

 left standing in the nurseries, remain healthy. The pruning of the roots 

 in transplanting has decreased too greatly the momentary capacity of water 

 absorption in the stock. Peaches on prune stock are also said to give no 

 especially permanent union-. The wood of the scion is said to turn red and 

 soon degenerate. I would add here an experiment with the grafting of 

 raspberries on Rosa canina^. Among rubus scions grafted by copulation, 

 I found two branches developing on one specimen, one of which bore four 

 normal raspberries. In the autumn, however, the scion died and, upon inves- 

 tigation, the coalescence was found to have been very slight. On the upper 

 part of the surface of copulation, only the stock had developed cicatrization 

 tissue. On the other hand, on the lower part of Rosa, as on Rubus, abundant 

 wound callus had been formed, showing normal processes of coalescence. 



1 Duhamel du Monceau, La physique des arbres 1758, II, p. 89. 



2 Pomolog. Monatshefte 1879, p. 370. 



3 Sorauer, P. Rubus auf Rosa. Zeitschr. f. Pflanzenkrankh. 1S9S, p. 227. 



