26 
with the scale insects sucking the juices, there is often consider¬ 
able damage done. The fungus will interfere with the process of 
assimilation by preventing the access of light and the escape of 
watery vapour and other gases. Indirectly this will hinder the 
growth of the tree and affect the production of bloom and of fruit. 
The leaves are less able to withstand the effects of drought or 
other unfavorable conditions, and if the young fruit is attacked, 
its development is hindered and generally it remains insipid. The 
injury done to the tree is not so readily realized by the grower as 
the damage done to the fruits. They are thereby rendered un¬ 
sightly and unsaleable, and have to bo thoroughly cleaned before 
marketing. This entails expense, and, as experiments have 
shown, interferes with the keeping quality of the fruit, apart from 
much of it being small in size and not properly ripened. Dr. 
Berleso has called attention to the serious effects of the disease 
on oranges and lemons in Italy. Not only are the fruits much 
smaller, and sometimes not produced at all, but the yield in af¬ 
fected groves may be reduced to one-tenth of their normal in a 
year. Keeping a tree in a healthy condition thus means a deal 
to the grower. The leaves do their work properly and encourage 
healthy root-action, the young wood is well developed, and the 
blossom is abundant; the fruit produced is allowed to ripen and 
attain its normal size and colour, and its keeping quality is main¬ 
tained, while the vitality of the tree itself is more abundant and 
more lasting. 
Causes —The Sooty Mould or black fungus is not a parasite, as 
has already been pointed out, and does not live at the expense of 
the plant, but by moans of the so-called honey-dew or sugary 
secretion of scale insects. The fungus itself belongs to the divi¬ 
sion in which the spores are produced in little bags or asci. This 
is the highest form of fructification, but there arc at least seven 
different stages or reproductive phases iu the life-history of this 
fungus. It is provided with means of multiplication and spread 
for all conceivable circumstances. If nourishment is scanty, then 
the joints of the filaments can break up and serve as reproductive 
bodies. Then the ends of the filaments can detach portions as 
coyiidia, to be carried by the agency of the wind, insects, birds, or 
animals to other trees. Several kinds of flask-shaped bodies 
produce their innumerable spores, aud finally the asci, with their 
ascospores, can withstand cold, heat, or drought, and renew the 
fungus when favorable conditions return. I hose different stages 
have been somewhat fully described and figured in a paper by me, 
printed in the Proceedings of the Linnean Society of iV.6. TF., 30th 
September, 1896, so that the subject need not be further enlarged 
upon here. Given a supply of food, and it is easily understood 
how the wind-borne spores can pass from tree to tree and from 
grove to grove, until an entire district is infected. 
