15 conidia.
" second day. 17 "
" third day. 27 "
" fourth day. 4 "
" fifth day. 9 "
"On none of the five nights did a single conidium alight on the slides.
This seemed to me to prove that during the day the conidia, through the
dryness of the atmosphere and the shaking of the leaves, became detatched
and wafted by the air; while during the night the moisture (in the form
of dew, and on one occasion of a slight and gently falling shower)
prevented the drying of the conidia, and thus rendered them less easy of
detachment.
"I determined the nature of the conidia (1) by comparing them with
authentic conidia directly removed from diseased plants; (2) by there
being attached to some of them portions of the characteristic
conidiaphores; and (3) by cultivating them in a moist chamber, the result
of which was, that five conidia, not having been immersed in the
glycerine, retained their vitality, which they showed by bursting and
producing zoospores in the manner characteristic of _Peronospora
infestans_."
INFLUENZA.
Let us look at another disease by the light of recent knowledge, viz.,
the epidemic influenza, concerning which I remember hearing much talk, as
a child, in 1847-48. There has been no epidemic of this disease in the
British Isles since 1847, but we may judge of its serious nature from the
computation of Peacock that in London alone 250,000 persons were stricken
down with it in the space of a few days.
Pages:
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110