FACTS NOT GENERALLY KNOWN 25 



and toe,' or 'anbury' can only attack cruciferous plants, 

 turnips, cabbages, etc. Corn mildew never attacks plants of 

 economic value, outside the various cereals. The above 

 statement naturally suggests, in the case of land known 

 to be infected by some particular fungus, the sowing of some 

 crop that cannot be attacked by the fungus known to be 

 present in the soil. This again means simply rotation of 

 crops. 



In connection with this subject, it may be pointed out that 

 a given disease is much favoured in its extension, when great 

 numbers of its host-plant are crowded together. Here again 

 it is in most instances practically impossible to avoid growing 

 large areas of the same kind of plant, as in the case of crops 

 generally, cereals, turnips, potatoes, etc. 



On the other hand, in some cases, trees of one kind only 

 are planted over a large area, especially larch-trees, whereas 

 if the wood consisted of a mixture of larch and other suitable 

 trees, the very destructive larch canker, caused by Dasyscypha 

 calycina, would be to a very considerable extent checked in 

 its career, and would not assume the proportions of an 

 epidemic. 



In many gardens and fields there is a corner reserved as a 

 dumping ground for rubbish in general, which in too many 

 instances is allowed to accumulate from year to year. Such 

 an accumulation of decaying vegetable matter serves as a 

 veritable hot-bed and nursery for many kinds of fungi, as is 

 proved by the presence of a considerable quantity of mould 

 and mycelium present, if the mass of decaying matter is 

 disturbed after six months' rest. Among other fungi Botrytis 

 rinerea is almost invariably present on decaying vegetable 

 matter, and this is one of the most universal and destruc- 

 tive of fungus parasites known. Undoubtedly many local 

 epidemics originate from spores produced on such accumu- 

 lations of dead and decaying plants. At the same time it is 

 necessary that plant remains should be collected some- 

 where, but to prevent danger, and at the same time en- 

 hance the value of the manure resulting from such accumu- 

 lations, a judicious sprinkling of lime or, better still, gas- 

 lime, would prevent the copious growth of fungi. 



I have on previous occasions stated that weeds of various 

 kinds growing on neglected borders of fields, headlands, 

 hedgerows, etc., harbour many kinds of fungi that are 

 capable of infecting the particular crop that may be growing 



