xxxvi.] POTATO DISEASE, II. PASSIVE STATE. 297 



before he was aware of Tulasne's discoveries. Professor 

 De Bary of Strasbourg, in 1863 (Ann. des Sc. Nat., ser. 

 iv., vol. xx.), made still further progress in detecting the 

 oospores or resting-spores of Peronospora. 



Oogonia or immature resting-spores are illustrated, 

 growing from the mycelium of the potato fungus within a 

 potato leaf, at S, T, U, and V, in Fig. 127. At S an 

 oogonium is seen intercalated within a thread of the 

 potato fungus ; at T and U the oogonia are terminal, 

 each with a second smaller body, termed an antheridium, 

 attached ; and at V another intercalated example is shown. 



FIG. 130. 



The sexual organs, or oogonia and antheridia of Peronospora infestans, 

 Mont. Enlarged 400 diameters. 



These bodies belong to the Artotrogus hydnosporus of Mon- 

 tagne. As the magnification of 100 diameters is insuffi- 

 cient to distinctly show the nature of these oogonia, we 

 have enlarged them to 400 diameters in Fig. 130. In each 

 of the four examples A represents an oogonium or cell in 

 which a female reproductive body, termed an oosphere, 

 is formed ; and each of the two bodies at BB is termed 

 an antheridium, or cell which contains the male repro- 

 ductive material. The oogonium may be roughly com 

 pared with a pistil in flowering plants, and the antheridium 



