pETHYBRiDGE — On tile Rottuiff of Potato Tuhers. 547 



appear that couidia are never (or extremely rsirely) developed on the myoelium 

 wlieii in air, or in a solid or gelatinous substratum, but only in watery 

 solutions. 



The conidia -when ripe are more or less ovate or inversely pear-shaped, 

 with a ratlier blunt or even somewhat flattened apes, and tliej' are not 

 provided with an apical papilla, as is the case in P. itifesfans, P. Ptiaseoti, &c. 

 They vary somewhat in size ; the average measurements of twent}' ripe ones 

 were : — Length, 3"2 /.i ; breadth (at the broadest point below the middle), 20;t(. 

 Occasionally larger and more irregularlj- shaped examples occur. They have 

 dense protoplasmic contents, and frequently a large central oil drop, and the 

 wall at the apex is slightly thicker and more hyaline than elsewhere. When 

 treated with a solution of iodine in potassium iodide, the contents appear to 

 undergo a slight contraction in the apical region, and the wall here becomes 

 clearer, as is shown in fig. 21, Plate XLIV. This figure also clearly shows 

 that thej' develop in sympodial fasliion, thus indicating the relationship of 

 the fungus to the genus Phytophthora. 



Q-roups of foiu' or live couidia close together, however, as illustrated, are 

 not very frequent. More often the 3'ounger couidia are borne on quite long 

 hyphae, which generally arise close below the points of origin of older ones ; 

 and cases were also observed where it was difficult or even impossible to make 

 out that the conidia were borne in a sympodial fashion. In such cases the 

 elongated hyphae beai'ing the conidia are usuall3'- considerabl}' more slender 

 than the general hyphae of the vegetative mycelium. Possibly when mature, 

 and when under suitable conditions, the conidia produce zoospores, but up to 

 the present tliis mode of germination has not been observed to occur. 

 Attempts to secure it by stimulation with oxygen gas, as was done bj' 

 Klebalm for P. Si/ringae, have been made, but up to the present the conidia 

 when treated thus have, if they have germinated at all, only produced a 

 hj'pha which usually becomes considerably branched near tlie apex of the 

 conidium, and which, together with its branches, does not ditier from ordinary 

 mycelium.' 



The following is a diagnosis in Latin of the new species of Pliytophtlwra : — 



PhytophHiora I'ri/f/iroscpticu n. sp. mycelio ramoso quoad partes receuti- 

 ores non septate quoad vetustiores niultiscptato vacuatoque oouidiis invei'si- 

 pyriformibus aut propemodum ovoideis s^'mpodialiter gonitis o'2f.t \ '20fi 

 anthoridiis terminalibus aut lateralibus aut intercalariis rotundis aut ovoideis 

 peuetratis ad vel iuxta bases suas oogoniis incipientibus quiv delude ex 

 partibus summis emerguut oogoniis pyriformibus super hyphas qura origine 



' Siuoe this was written typical zoospores havo been oliservotl. 



i M -i 



