4 MULBERRY DISEASE, 
mulberry. The tree is not uncommon in the cultivated parts of 
the Valley, but is not likely to play much part in disseminating 
the disease. 
DESCRIPTION OF THE PARASITE. 
Tne body of the parasite, as of fungi generally, is composed of 
numerous branching threads. These penetrate throughout the 
tissues of the attacked portion of the branch, where they are natural- 
ly hidden from view ; they can only be seen on examining micros- 
copically very thin sections of the wood, such as that, a portion of 
which is shown in Plate II, fig. 2. The examination of such 
sections shows that every part of the branch-tissues becomes 
infected, pith, wood, bast and bark. Towards the centre of the 
branch the threads are mostly colourless, while nearer the surface 
they are deep brown. They vary greatly in size, from large thick- 
walled brown threads, such as those in the iarge vessel of the wood 
to the left in fig. 2, to fine colourless ones in the small cells of the 
inner part of the wood and in the pith, They grow from cell to 
cell with the greatest ease, boring through even the thick walls 
of the large vessels. ‘Towards the surface of the wood they begin 
to accumulate into twisted, brown masses. ‘These increase in the 
inner layers of the bark, and it may be noticed that whereas the 
walls of the wood-cells are not materially altered, those of the bast 
and inner bark are largely destroyed by the dense fungus growth. 
Immediately under the cork cells of the bark, numerous solid 
cushions of fungus tissue are formed by the continued branching 
and intertwining of masses of threads. These become divided by 
cross walls into rounded or angular cells, whose appearance in 
section under the microscope is shown in the central part of fig. 1, 
plate Il. Along the margin of these cushions, spores are produced 
in large numbers as shown in the figure, and, by the continued 
growth of cushions and spores, the bark is ruptured. Hence each 
of the ruptured areas on the bark visible in the photograph in Plate 
I, fig 1, is lined by a black cushion of the fungus similar to 
that shown in vertical section in the figure, from the surface of 
which quantities of spores are set free into the air. The mode of 
