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‘are to spring frosts, to cold winds, etc., the fohage does not 
develop fully for some six or eight weeks. _ The result of this 
tardy development is that the immature fohage is exposed for 
3 lengthy period to the attacks of certain insects such as the 
larch aphis (Chermes laricis). As the fungus can only find its 
way into the larch through wounds in its tissues one can readily 
understand that the trees growing in the lowlands are far more 
liable to its attacks than those of the highlands where the 
foliage is only in a sufficiently succulent condition to tempt the 
aphis for a brief period. . 
A second example is provided by Pythium de Baryanum the 
fungus responsible for the “damping off” of seedlings. This 
parasite 1s capable of attacking many kinds of seedlings and 
rapidly reducing them to a slimy mass. It is particularly 
common on the seedlings of Cruciferous plants, the favourite 
host being perhaps the common cress. If seed beds of this 
plant be thickly sown and kept thoroughly moist one can 
generally count on an outbreak of the disease. By simply 
altering the external conditions by growing the seedlings in a 
dry atmosphere the ravages of this fungus can readily be kept 
under control. This same factor, excessive moistness of the 
atmosphere 1s responsible for the rapid spreading of many of 
the diseases which attack plants cultivated under glass. Many 
a crop of cucumbers for instance has been utterly destroyed by 
gardeners failing to realize that a thoroughly moist, warm 
atmosphere is far more favourable to the growth of Botrytis 
cmerea than that of the crop they intend to grow. 
Under this same heading of avoiding conditions known to 
be favourable for the spread of fungoid diseases we may include 
the subject of the proper treatment of wounds in plant tissues. 
A considerable number of fungi can only bring about the in- 
fection of their host plants through abrasions in the cuticle or 
the corky protective layers. As long as these tissues are sound 
the plant remains altogether free from the attacks of such 
wound-parasites. A broken branch, bruises caused by hail- 
stones or by the rubbing of animals, etc., the wounds caused 
by pruning, by careless fruit-picking and so on, may all serve as 
points of entry for a fungus. Such wounds, if small, are readily 
healed by the formation. of callus, but where large snags are 
left by breakages or by bad pruning, the healing process may 
take several years to complete, and meanwhile the exposed 
surface 1s able to become infected by various wood-destroying 
Parasites. Any exposed surfaces should therefore be treated in 
such a way as to reduce this chance to a minimum. The best 
method is to pare the exposed surface until it is smooth, dress 
it with a dilute solution of corrosive sublimate, and when this 
has thoroughly dried in to cover the wound with hot. tar. 









