Proceedings 79 
One of the most frequent causes of disease in plants is 
the fungus that causes the “Lily disease.” Like many other 
fungi it has a somewhat complicated life history consisting 
of two distinct stages: the resting stage when a Sclerotium 
is formed which sometimes produces a cup shaped fungus 
called Sclerotinia, and a summer stage which is known as 
the Botrytis or conidial stage. 
If we take the summer form which is far the commonest, 
and examine the injured lily on which the fungus has 
settled, we find growing from the surface of the damaged 
organ a tiny forest of delicate, dark coloured stalks which 
can easily be distinguished with a hand-lens, each stalk 
being crowned by a greyish-looking head formed of a 
multitude of minute, light-coloured, oval-shaped bodies 
called spores or conidia. The terms spore and conidium 
are used for the reproductive bodies of the fungus, just as 
seed is used for the higher plants. ‘The conidia of Botrytis 
do not require any resting period. If they alight on a 
suitable substratum, such as moist rotting vegetation, or 
even a drop of water, germination takes place at once. 
They can be easily cultivated on gelatine mixed with prune 
juice and the whole process of growth can be watched by 
the aid of a microscope. 
The conidia respond to the moist environment, and 
in a few hours they are seen to have pushed out a tube or 
even more than one. The tube elongates to a filament 
and imbibes nourishment more especially at the growing 
point. It continues growing and branching till there is 
formed a confused tangle of thread-like filaments; each 
individual filament is termed a hypha, the whole mass of 
hyphe is known as the mycelium of the fungus. From 
any point of the mycelium there may rise vertical stalks, 
which are stronger and darker in colour then the creeping 
filaments. They are the fertile hyphz, the conidiophores 
or conidia-bearers and attain a height of one or more 
millimetres. At the lip of the stalk, a series of short stout 
branches or projections are formed which are studded 
with the oval-shaped conidia. If the food supply is abun- 
dant and atmospheric conditions favourable, the stalk sheds 
