206 ' ON THE PERONOSPOR^. 



described as Artotrogiis^ found by Montague in spent potatoes, he 

 considered the two to be identical. 



Early in 1876 De Bary's investigations were made known. 

 He also found certain bodies like oospores in decayed Potato 

 tubers, but considered them as belonging to the genus Pythium^ 

 especially as he w^as able to grow fresh crops of mycelium from 

 them on the legs of dead flies, bodies of mites, etc. He called 

 the species P. vexans, in consideration of the trouble it had given 

 him, and thought that the Artotrogus of Montague belonged to a 

 still undetermined fungus. He considered that the perennial 

 mycelium of the Potato disease occasionally discharged the 

 function of hibernation, when the oospores were not found. In 

 this case the spawn of the Potato fungus would live through the 

 winter in the tubers of the Potato, and be propagated in the spring 

 by means of diseased tubers, and of tubers healthy at time of 

 planting, but destined soon to become diseased from others. He 

 thinks there are two methods by which the conidia may pass from 

 the tuber to the haulm, i. — The conidia may be formed in the 

 tuber, and carried up to the foliage in course of growth. 2. — The 

 mycelium may grow from the tubers up through the haulm and 

 foliage, and there produce conidia. De Bary seemed to think 

 that the fungus found some resting place external to, and indepen- 

 dent of the Potato plant, an arrangement by no means uncommon 

 amongst fungi. He suggested the Nat. Ord. Scrophulaciace^ 

 as the place where the resting spores might be found, an idea 

 derived from English botanists. The Secretary of the Royal 

 Agricultural Society had suggested also that Clover or Straw might 

 be the host in question. 



In July, 1876, Worthington Smith pubHshed a further series of 

 observations. He had, with untiring energy, kept alive and 

 constantly under observation, the bodies he discovered in July, 

 1875. The only change he noticed for a long time was that they 

 increased in size, till they became nearly four times their original 

 bulk, but at the beginning of May he began to see signs of 

 germination. At this time many of the oospores proved effete, 

 but in some the contents were broken up into zoospores, which 

 were discharged in an active condition, and after swarming 

 became quiescent, and emitted filaments of mycelium. In some 



