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plant diseases comprises those which attack fruits. In 
this lecture we shall consider the most common disease of 
seedlings which is known as the “ Damping off” disease. 
Before dealing in detail with this, however, let me 
recall some of the more essential features in the structure, 
nutrition and life history of the more common fungi, facts 
with which you are no doubt, to some extent, already 
familiar. In any of the fields and lanes around our large 
towns, especially in autumn, it is possible to find examples 
of the larger fungi such as mushrooms and _ toadstools. 
Whilst the colour and form of the part which we see above 
ground are often striking, in reality this is only the repro- 
ductive part of the toadstool or mushroom plant, just as 
much as the flower and fruit are the reproductive parts of 
the higher plant. It is true that the mushroom as we 
generally see it, appears above ground, sheds its spores 
and decays all within a few weeks; but the vegetative part 
of the plant lives in the ground for a very considerable 
time before it enters on the reproductive phase. 
The bricks of so-called mushroom spawn contain 
quantities of fine interlacing threads of fungus, in manure 
which are really the vegetative part of the mushroom. 
Under the microscope these filaments are seen to consist 
of long branched tubes. These tubes are divided up into 
chambers or cells by cross partitions, and each cell is 
lined with the jelly-like semi-transparent living substance, 
protoplasm. Within this are drops of water and oil as 
well as certain denser granules, but filaments of fungi 
never contain the green colouring matter found in higher 
plants. The protoplasm is the living part of the cell, 
and food material is taken in from the soil or manure 
through the protecting cell membrane. Such food 
material often appears stored in the tubes as drops of oil. 
Although the filaments of the vegetating mushroom. 
plant are not bound together into a complex plant body 
like the cells of flowering plants, yet the loosely inter- 
woven threads behave as a whole, and after weeks or 
months of vegetative growth give rise to the definite fruit 
bodies consisting of numberless aggregated filaments. 
‘These reproductive bodies usually possess a stalk bearing 
an expanded cap from the under side of which project the 
radiating gills. Upon the surface of the gills are borne 
large numbers of minute round or oval spores, Each 
spore is really a single tiny cell so small that it can only 
