ECONOMIC MYCOLOGY. 
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evidence at present to hand indicates that these have a beneficial 
effect in checking fungoid ravages. 
The chemical effects of lime upon the soil have received great 
attention, but its action in neutralizing soil-acidity is not sufficiently 
recognized. In the case of Plasmodiophora this is a most important 
factor. Since the middle of last century it has been noted that 
" fmger-and-toe " is practically absent from calcareous soils, and 
that dressings with lime tend to check this disease. Also it has been 
noted that manures which tend to increase the acidity of the soil 
favour its development. This problem has received solution by the 
work of G. Potts, carried out in the Botanical Laboratories at New- 
castle and at Halle (Salle), by which it was demonstrated that alkalinity 
of the soil, from any cause, secured the immunity of the host from 
attack by the parasite. His experiments also showed that the soil 
calcium has not necessarily any relation to the disease. I have shown 
that below a depth of four to five inches the spores of Plasmodiophora 
are killed, or are at least inoperative. Hence a sufficient dressing of 
lime should be given to render the soil alkaline to this depth. The 
acidity of the soil varies from field to field, and also is not constant 
throughout the year. It is thus impossible to predict how much lime 
should be applied in any given case, and field experiments following 
up Potts's work, to test the power of lime to neutralize the acid in 
the soil, are much needed as a means of saving our cruciferous crops 
from this most destructive parasite. How far soil acidity or alkalinity 
are factors in other plant diseases is another of the points awaiting 
elucidation. 
It is a matter for further research to determine how far such 
operations as transpiration, respiration, &c., may be modified by 
manurial treatment, and within what limits it may so alter the con- 
stituents of the cell-sap as to be usefully employed as a prophylactic 
treatment. 
Great strides have been made in recent years towards a recognition 
of the needs of Economic Mycology, which have naturally shown 
how much more remains to be accomplished. 
The Destructive Insect and Pests Act has been put in operation 
by the Board of Agriculture as a necessary means of coping with the 
devastating spread of certain diseases in this country. This has 
drawn the attention of cultivators to the prevalence of plant diseases, 
has shown the value of co-operation in preventing the dispersal of 
parasitic attacks, and has emphasized the need for the minute study 
of the fungus flora of the crops. For example, had Sphaerotheca 
Mors-uvae and Chrysophlyctis (Synchytnum) endobiotica only been 
rigidly dealt with on their first appearance, how much destruction 
might have been saved ! 
The establishment of the Phytopathological Laboratory at Kew, 
in touch with the mycologists in all parts of the Empire, is another 
forward step which cannot fail to be of the utmost importance to our 
Colonies and at home. But more is required. Phytopathological 
VOL. XLII. V 
