344 
growing in the open with spores obtained from the same kinds 
suffering from an epidemic when grown under glass. A good 
or the above reasons I am led to consider that attention to fungi 
alone is but a poor equipment for a post as plant pathologist, 
and will not ledd to a reduction of the losses caused indirectly by 
fungi, which can never be exterminated. 
Among the known primary agents which enable the large class of 
fungi known as wound-parasites or facultative parasites to gain an 
entrance into plant tissues may be enumerated insects of various 
inds, which by eating, and more especially by simply puncturing ~ 
the tissues, enable the germ-tubes of spores to gain a foothold, at 
first by obtaining food from the injured cells and living as sapro- 
phytes, then gradually assuming a parasitic habit and invading the 
living tissues of the host-plant. In many instances not only do 
insects—aphides, mites, scale-insects, &c., enable the fungus to gain 
an entrance into a plant, but they also unconsciously carry and 
deposit the spores of the fungus in the punctures made. Injury 
caused to young leaves and tender shoots by hail is frequently 
followed by an epidemic, fungus spores germinating readily on the 
bruised tissues. Climatic conditions are a most important factor in 
determining the presence or absence of epidemics due to fungi; 
marked contrasts in temperature during the spring months invari- 
ably mean an excess of injury caused by fungi, whereas an equable 
temperature during the same period is marked by a comparative 
absence of disease. The same applies if extremes of temperature 
occur between day and night im conservatories, &c. I have 
frequently cultivated fungi, Botrytis, Fusarium, Trichothecium, 
that have commenced their parasitic career in old, partly 
decomposed nodules on the roots of leguminous plants. 
e above remarks, of course, apply to the great number of fungi 
oscillating between parasites and saprophytes, and which only become 
true parasites under special circumstances. The extension of disease 
due to fungi is favoured in many ways by modern methods of culti- 
vation as the marked extension of fungi in space is facilitated by rapid 
transit. In this respect opportunity is a factor of primary importance. 
I think it may be stated, without fear of contradiction, that no living 
