I13 
bating the spread of disease. All cases cannot be satisfactorily 
dealt with, but in the majority the evil can at least be mitigated 
to some extent. 
The economic importance of these plant diseases depends on 
the intensity of the attack and the value of the host plant. A 
cereal crop for instance may be but slightly attacked by one 
of its rust parasites and comparatively little damage may result, 
whilst a serious attack may not only mean a greatly diminished 
yield but also a serious depreciation in the value of the grain. 
' In the same way Phytophthora infestans may in some seasons 
be practically harmless, whilst in others, as in 1845, its attack 
may be so virulent that the potato crop is completely destroyed 
throughout the country. Obviously such external conditions 
are beyond our control, nevertheless much can be done to mini- 
mize the losses these fungoid parasites cause. 
When we attempt to obtain some idea of the actual magni- 
tude of such losses we can only find the most fragmentary data, 
yet they are quite sufficient to show us the importance of the 
issues at stake. A few well-worn statistics may be quoted 
here. According to the report issued by the International 
Phytological Commission in 1893 the cereal rusts alone cost 
Prussia over 420,900,000; in other words, one-third of the 
total crop of the country was destroyed. These same rusts 
cost Australia £2,500,000 in 1890-1. In the following year, 
1892, a vine disease was responsible for the loss of a similar 
amount in California. When one adds to these figures the un- 
recorded losses due to potato disease, to smuts in cereals, to 
decay in fruits, in timber and so on, one begins to realize that 
the year’s bill must be an enormous one. Yet one often hears 
the farmer or horticulturalist say that such and such a disease is 
of no practical importance. It would be better with them if 
this were really the case, but those who have the opportunity of 
watching their crops are driven to recognise that the small and 
generally unrecognised losses in their cumulative results are as 
serious as those for which statistics are obtainable. 
In countries where the importance of the proper care of farm 
and garden crops is recognised such knowledge has led to State 
supervision of the cultivation of certain crops and regulations 
ate issued for combating the parasites which attack them, 
penalties being imposed for the non-fulfilment of the precau- 
tions demanded. How far State interference is practicable in 
this country is an open question, though of its value in some 
Cases there can be no doubt. Without discussing the possibili- 
lies of checking the importation and wholesale dissemination 
of new parasitic forms from abroad, which as a matter of fact is 
Prevented in the case of farm animals, let us turn to the efforts 
actually made in this country to minimize the losses due to the 
