152 ON SEXUAL REPRODUCTION IN THE PERONOSPORA. 



quite similar to those which are engendered in the sporangia without 

 previous fecundation. Immediately after this division, the herni- 

 ary prominence, which we mentioned as issuing from the epispore, 

 increases into a globose, and very thin bladder, into which the 

 zoospores pass to commence their agile movements, but this vesicle 

 soon dissolves, in order to allow the zoospores to disperse. 



In Peronospora valerianellce , and the most nearly allied species, 

 the oospore, when germinating on a damp body (but not in water) 

 emits a tubular filament, the membrane of which proceeds from the 

 inner layer of the endospore, and which has broken the exterior 

 integument of the spore. The germ elongates considerably, rami- 

 fies, and assumes completely the appearance of the mycelium of the 

 Peronospora. Its introduction into the nourishing plant has not 

 yet been observed.* 



SEXUAL REPRODUCTION IN THE ERYSIPHEI. 



By Dr. Anton de Bary. 



Amongst the Fungi whose sexual organs are known, we must 

 certainly place Erysiphe, according to the researches which I pub- 

 lished on the fructification of the Ascomycetes (Leipzig, 1863). 

 The fecundated oogonium or oocyst in Erysiphe does not develope 

 into a simple oospore, but into a complex perithecium, which en- 

 closes the thecre, or sporidia-bearing cells. The mycelium of Ery- 

 siphe cichoracearum, like that of other species, consists of branched 

 filaments crossed in all directions, which adhere as they climb to 

 the epidermis of the plant on which the fungus lives as a parasite. 

 The perithecia are engendered where two filaments cross each other. 

 These swell slightly at this point, and each emits a process which 

 imitates a nascent branch, and remains upright on the surface of 

 the epidermis. The process developed from the inferior filament 

 soon acquires an oval form, and a diameter double that of this 

 filament, then it becomes isolated from it by a septum, and con- 

 stitutes a distinct cell, which I qualify as an oocyst. The appen- 

 dage which proceeds from the superior filament always adheres 

 intimately to this cell, and elongates into a slender cylindrical tube, 

 which terminates in an obtuse manner at the summit of the same 

 cell. At its base it is also limited by a septum, and soon after- 

 wards another septum appears a little below its extremity, at a 

 point intimated beforehand by a slight strangulation. This new 

 septum completes a terminal, short, and obtuse cell (the anthe- 

 ridium), w T hich thus becomes borne on a narrow tube like a sort of 

 pedicel. Immediately after the formation of the antheridium, new 

 productions show themselves, both around the oocyst and within it. 



* More ample details will be found in " Botan. Zeitung, 1861," p. 89, and 

 "Ann. des. Sci. Nat.," ser. 4, vol. xx. (1862;. 



