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Transactions of the Society . 
and a greater number of sporopliores than others that were developed 
throughout the entire life-cycle on the same host-plant. Secondary 
spores formed in pure water invariably produced smaller patches of 
disease than those formed in a nutritive solution, and in many 
instances the germ-tubes of such secondary spores were quite rudi- 
mentary, and never penetrated into the tissues of the host-plant. 
When spores are sown in water containing 1 per cent, of glycerin 
a single sporophore is almost invariably formed at one end of the 
spore, and this bears at its apex a comparatively large head of 
catenulate secondary spores. 
The difference produced by spores germinating in different 
nutritive solutions manifested itself in the relative development of 
the germ-tubes, and the proportion of secondary spores produced ; 
the size, form, colour, and power of germination of the secondary 
spores being the same in all the cultures. 
Throughout the summer months the spores germinate as soon as 
mature, at the ordinary temperature of the air ; but the later batches 
of spores produced in September and October will not germinate, or 
very feebly, at the temperature of the air ; such spores remain passive 
during the winter, and germinate the following spring. Nevertheless 
these are not resting spores — in the ordinary sense of the term — but 
will germinate at any period throughout the winter, provided the 
temperature be sufficiently high. 
The spores will not germinate at all in water containing a 1 per 
cent, solution of either of the following substances: — sulphate of 
copper, oxalic acid, picric acid, tartaric acid. These substances are 
not in like manner detrimental to the germination of all kinds of 
spores : Penicillium glaucum, as stated by De Wevre * and corro- 
borated by myself, attains its full development in water containing 
1 per cent, of tartaric acid. 
During the four years of observation on the same beds of host- 
plants, I have been very much struck by the perfect freedom from 
disease of certain individuals, growing in the midst of others that 
were attacked by the parasite, and I find on experimenting that those 
specimens which are not affected in a state of nature, cannot be 
artificially inoculated by placing germinating secondary spores on 
moistened portions of the leaves, as can easily be done in the case of 
plants that already show symptoms of the disease. On one particular 
clump of plants of Convallaria majalis , I have not observed a trace of 
the fungus for four years ; neither have I succeeded in artificially 
inoculating these particular plants, although repeated attempts have 
been made for this purpose during the past two years ; whereas I have 
succeeded in infecting plants of the same species that have already 
shown symptoms of the disease, with portions of the same infecting 
material used in experimenting upon the impregnable individuals. 
* Bull. Soc. Roy. Bot. Belg„ xxx. p. 115. 
