Communications. 277 



THE POTATO FUNGUS — GERMINATION OF THE 



RESTING SPORES. 



By WoKTHiNGTON G. Smith, F. L. S. 



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 peiiod as a whole 

 year. Last July, I obtained the oospores or resting spores by keep- 

 ing potato-leaves and tubers continually moist. For many years 

 past moisture has been well known to greatly excite the growth 

 of Peronospora infestans^ and De Barry in his recent essay classes 

 the potato fungus with "other water fungi." Mr. C. Edmund 

 Bromne, of Betheaston, who is known as one of the first crypto- 

 gamic botanists of this country, repeated my experiments in the 

 following manner: He selected potato leaves badly infested with 

 Peronospora, partly crushed them, and placed them in a saucer 

 of water underneath a bell-glass. The saucer was kept in a slop- 

 ing position, so that the leaves (being partly submerged) were al- 

 lowed 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 .«pores were in every way identical to mine, and could only 

 belong to the Peronosporeic or Saprolegnietc, because similar bodies 

 are unknown to other families of fungi. The first-named family 

 has jointed threads, the eecond 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 are no other Pero- 

 nospora than P. infestans known to grow on 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 importance to the jointed threads because De Barry, 

 when he figures Artogrotus from ' Montague's original specimens, 

 shows the threads with many septa. From the first I said that 



