18 
THE POTATO FUNGUS. 
GERMINATION OF THE RESTING-SPORES. 
By Worthington G. Smith, F.L.S. 
With Plates 70 to 73.* 
Before describing the germination of the resting-spores of the 
fungus which causes the potato disease, it will be well to briefly 
state how these resting-spores were obtained, and how preserved 
alive in a state of hybernation for so long a period as a wliole 
year. Readers of the Gardeners' Chronicle need not be reminded 
that I last July obtained the oospores or resting-spores by keeping 
potato leaves and tubers continually moist. For many years past 
moisture has been well known to be capable of gn'atly exciting 
the growth of Peronospora infestans, and De Bary, in his recent 
essays, classes the potato fungus (p. 242) with ‘‘ other water fungi.” 
Mr. C. Edmund Broome, of Batheaston, who is known as one of 
the flrst cryptogamic botanists of this country, rejDeated my 
experiments in the following manner: — He selected potato leaves 
badly infected with Peronospora, partly crushed them, and placed 
them in a saucer of water under a bell-glass. The saucer was 
kept in a sloping position, so that the leaves (being partly sub- 
merged) were allowed to absorb the water naturally. The result 
was that he obtained an enormous number of resting-s])ores in all 
parts of the leaves, many being vv'ithin the spiral vessels and hairs. 
These resting-spores were in every way identical with mine, and 
they could only belong to the Peronosporea? or Saprolcgnia?, 
because similar bodies are unknown in other families of fungi. 
The first-named family has jointed threads, the second bears 
threads without joints ; now as the threads seen by me, and last 
year illustrated in connection with the resting-spores, had jointed 
threads, they must belong to Peronosporea, and not to Saprolegnia. 
x^s there is no other Peronospora than P. infestans known to 
grow upon the potato plant, it is clear that the resting-spores 
cannot rationally be referred to any other than the potato fungus. 
Added to this, I last year saw the secondary bodies clearly 
growing from the Peronospora threads. I attach great im- 
portance to the jointed threads, because De Bary, when he figures 
Artotrogus from Montague’s original specimen ” {Researches, p. 
258), shows the threads with many septa. From the first I hrve 
said that Montagne’s i\rtotrogus and the bodies discovered by me 
are the same. That both belong to Peronospora the sequel proves. 
It was of the highest importance that these resting-spores 
should be preserved alive till the time arrived for their renewed 
activity, and with this purpose in view I preserved the material 
in which the resting-spores were present in sealed bottles, each 
* By kind permission of the proprietors of the “ Gardener’s Chronicle.” 
