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III. — The Potato Fungus. Germination of the Besting Scores. 
By WoRTHiNGTON G. Smith, F.L.S. 
Plates CLI, CLII., OLIII., and CLIV. 
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 whole year. 
Eeaders 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 greatly exciting the growth of Peronospora 
infestans, and De Bary in his recent essay classes the Potato 
fungus* with "other water fungi." Mr. C. Edmund Broome, of 
Batheaston, who is known as one of the first cryptogamic botanists 
of this country, repeated 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 underneath a 
bell-glass. The saucer was kept in a sloping position, so that the 
leaves (being partly submerged) were allowed to absorb the water 
naturally. The result was that he obtained an enormous number 
of resting spores in all parts of the leaves, many being within the 
spiral vessels and hairs. These resting spores were in every way 
identical with mine, and they could only belong to the Peronosporese 
or Saprolegniese, 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 Peronospora, and not to 
Saprolegnia. As 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. 1 attach great importance 
to the jointed threads, because De Bary, when he figures Artotrogus 
from " Montague's original specimen," f shows the threads with 
many septa. From the first I have said that Montague's Arto- 
trogus and the bodies discovered by me are the same. That both 
belong to Peronospora the sequel will prove. 
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 
* 'Researches,' p. 242. t Ibid. p. 258. 
