Marshall Ward. — On a lily-disease. 367 
is only necessary to take up any systematic work on the 
group 1 to see what confusion prevails as to their nomen- 
clature and classification. De Bary has shown that Peziza 
Sclerotiorum has probably received a different name for almost 
every species of host-plant on which it has been found, and it 
is in the highest degree probable that various species, good 
and bad, now pass under different names in England and on 
the Continent. 
In conclusion, then, the lil y-Botrytis is probably a gonidial 
stage in the life-history of some Peziza ; whether the alterna- 
tive form is developed on some other plant, or whether it is 
lost, cannot be said. It is quite conceivable, however, that in 
consequence of their pronounced parasitism this fungus and 
Phytophthora infestans may have lost their alternative form. 
The attempt may now be made to give a general account of 
the disease, and to see how far we can explain the epidemic 
nature of this year’s attack, from what is known so far. 
It is quite certain, at the outset, that the fungus itself was 
present in the lily-beds in my garden in 1886 and 1887 : why 
then did it remain sporadic during those years, and become 
epidemic in 1888? I think the explanation is to be sought 
along the following lines. 
The parasitism of the fungus depends, as we have seen, in 
the first place on its power to excrete a ferment which softens 
cell-walls, and enables the hyphae to feed on their substance : 
this ferment acts best in a slightlyacid medium, and it requires 
water, if for no other purpose, to enable the ferment to diffuse, 
but also because the more watery the cellulose the more easily 
it is dissolved. 
Now if we compare the meteorological records for 1887 and 
1888 2 , especially for June, July, and August, the period of 
active development of the flower-axes of the lilies, it will 
be found that, in the district referred to, the summer of 1887 
was particularly hot and dry, and the lilies that year produced 
1 E. g. Phillips’ monograph (British Discomycetes) in the International Scientific 
Series (1887), which, by-the-bye, contains no reference to Botrytis or gonidial 
forms that I can discover. 2 See Table and remarks in Appendix on page 370. 
