562 
Notes. 
acts of infection and incubation occupy about ten days, and many 
exigencies may prevent the germination of the spores, the entry 
of the germ-tubes into the stomata or the successful growth of the 
mycelium in the tissues. 
Experiments go to show that the lack of certain minerals- — e.g. 
potassium or phosphates — cause a starvation of the Fungus ; partial 
etiolation of the host, or any other hindrance to free nutrition, 
assimilation, transpiration, &c., also act detrimentally to the well-being 
of the mycelium. 
Every degree of virulence of attack seems to be shown by the 
spores in their germ-tubes, either on different varieties or species 
of host, or on the same host in different conditions. 
It appears that in certain cases the germ-tubes may kill the tissues, 
and cause them to turn black and shrivel up as if corroded. In such 
cases the parasite can make no further progress, and infection fails. 
In other cases a mycelium is developed, but lies dormant and produces 
no spores ; we may compare the Fungus in this case to a plant in poor 
soil, or suffering from drought, &c. 
Seedlings with ‘spears’ only a millimetre or two high can be 
infected by applying spores to the ‘ dew-drops ’ issuing from the 
water-stomata at the apex of the first leaf. 
Cambridge, 
July 27, 1901. 
H. MARSHALL WARD. 
