138 Butlr—A Study on Gummosis of Prunus and Citrus, with 
sacrificing, even at some hazard, a certain amount of resistance power for 
better affinity. It should also be pointed out that in soils in which 
C. Limonum on their own roots are only slightly affected by gummosis, 
there is no object in using the very resistant Citrus as stocks; the question 
of affinity should alone be considered. . 
3. Moderating growth by root-pruning. This method | of preventing 
gummosis is mentioned by M'Intosh and ger se is unobjectionable. The 
difficulties of applying it and the complications liable to result from its 
injudicious use are, however, sufficient to prevent it being ever more than 
a gardener’s palliative. 
4. Amendments. The amendment mostly employed in preventing 
gummosis is lime, and its use is advocated by a number of horticulturists. 
Its beneficial action is probably due to the increased porosity of the soil 
following the flocculation of the clay. Salt has also been recommended by 
Van Hecke, who observed in China a peach orchard which, though covered 
at flood-tide by salt water, remained quite free from gummosis, whereas an 
orchard irrigated by river water was badly affected. Van Hecke was 
particularly struck by the fine appearance of the orchard submerged at 
flood-tide, and, upon his return to Belgium, tried the following instructive 
experiment. He selected’ four peach-trees growing under similar conditions, 
and treated them as follows immediately before the opening of the buds :— 
No. 1. Received 1,500 grm. salt. 
No. 2. Received 1,000 grm. salt. 
No. 3. Received 500 grm. salt. 
No. 4. Received © grm. salt (witness). 
The result of the experiment was most striking; the witness gummed 
considerably and even lost several branches, the trees that received one 
half and one kilo of salt respectively were only very slightly diseased, and 
the remaining tree was not affected. Van Hecke’s observation and subse- 
quent experiment remind one of the remark of Downing’s that salt is one 
of the best fertilizers for the plum.? Salt as a preventive of gummosis could 
be made, it seems to me, the subject of further inquiry. 
Besides the major methods of preventing gummosis just described, there 
are several minor ones that are deserving of mention. 
1. In the district of Carcagente,? Spain, where the soil is somewhat 
sandy and very permeable, and the orchards are presumably not over irri- 
gated, as the water has to be drawn from rather deep wells, the oranges, 
grafted on limes or citrons, are planted sufficiently deeply for the scion to 
* Hecke, E,van: Le sel de enisine et les arbres fruitiers » noyau. Journ. des Soc. Agric. 
Brabant et Hainault, 30 mars 1907. 
? Downing, A. J.: Fruits and Fruit Trees of America, p. 266, ed. 1850. 
3 Vide Trabut, L.: L’Oranger en Algérie. Direction de Agriculture gouv. gén, Algérie, 
Bull. 44, 68, 1908. 
