280 AN INQUIRY INTO THE CAUSES OF THE DEATH OF
young branches that exhibit a shrivelled appearance, coarse
hyphal threads are abundant. These occur some time before
the fungus reaches its perfect form, and before the leaves have
withered.
The appearance of a branch depends on the age and develop-
ment of the fungus (figs. 7 and 8). In an early stage it is covered
with an immense number of pustules which show the epiderm
tightly extended over the elevations. After a period the pustules
burst and disclose a mass of hyphal threads which produce conidio-
Figs. 7 and 8. Two sides of the same branch showing the different stages
in the development of the disease.
spores. Later on there is a change of colour, the pustules
becoming very dark and even black. Sections of the older ones
show another set of spores, the spermatia, long, narrow, hyaline,
slightly curved bodies. At the perfect stage of this fungus flask-