386 
PROCEEDINGS OE SECTION D. 
The mycelium which flourishes within the substance of the plant 
infested is capable of producing larger globose bodies, chiefly within 
the stems, concealed from external view. These globose bodies secrete 
a thick envelope, mostly of a brownish colour, and after development 
they remain in a state of rest within the stems during the winter. So 
that old stems of plants, wlvich are infested with the mould during the 
autumn, conceal within themselves during the winter a large number 
of these £< resting spares.” As the old stems rot and decay the resting 
spores are set free in the spring, and then a period of activity com- 
mences. The contents of these globose bodies become differentiated 
into a large number of zoospores, which ultimately escape, by a 
rupture of the thick envelope, armed with vibratile cilia, and in all 
respects like the zoospores which are developed from the conidia. 
These active zoospores swarm over the damp soil, and are carried by 
the spring rains into proximity with the young seedling leaves of the 
new "crop of host plants ; then the cilia are absorbed, germination 
commences, the delicate threads of mycelium enter the nearest 
stomata, and infection results. In this way, in addition to the spread 
of the infection from conidia in summer and autumn, provision is made 
for an attack upon seedlings in the spring. It will be inferred that, 
in order to check the spread of these diseases, the conidia must be 
destroyed in the autumn, to prevent their extension to healthy plants ; 
and the destruction of all rotting debris must be carried out during 
the winter, so as to extirpate all the concealed resting spores, and 
thus prevent the infection of seedlings in the spring. 
Erom these details it will be evident that plants once attacked 
by endophytal parasites are in themselves hopeless. No external 
application can destroy organisms which it cannot reach, or, if they 
could be destroyed, no manipulation can replace the disorganised 
tissues. Hence," then, all efforts should be directed towards the 
destruction of the conidia and resting spores, in order to stamp out 
the disease at its source, and prevent the future infection of healthy 
plants. The application of spraying to plants apparently without 
disease would be done as a preventative, in order to destroy at once 
any germs which might be brought into contact with the foliage ; and 
the destruction of all infected material would limit the local sources of 
infection. With an intelligent appreciation of the objects which have 
to be attained, the cultivator may accomplish a great deal in the way 
of prevention, even though he may be helpless to effect a cure. It 
will be seen how 7 much of this depends upon an accurate diagnosis of 
the disease. 
There are many other forms of endophytal parasites, and the life 
history of some of these is still obscure. In the majority of them 
only a conidial fructification is yet known, and the internal tissues do 
not appear to he so absorbed and destroyed as in the case of the “rot 
moulds” ; but in such black moulds as the “apple and pear scab” the 
mycelium appears to be perennial, and produces a fresh crop of conidia 
each successive year. There is some evidence that this disease is deep 
seated and hereditary, and, if so, it is doubtful whether any amount of 
external application will result in a perfect cure. The genus Glao- 
sporium includes many species which are very destructive, but often 
they seem to be localised, and the mycelium may not pass internally 
to other parts. This can only be ascertained by closer investigation. 
