xxix.] MILDEW OF PARSNIPS. 243 



states that tlie mycelium belonging to the two fungi is 

 different, and that the oospores of Protomyces contain great 

 numbers of very minute slightly oscillating spores, which 

 escape from the expelled inner membrane as in Cysto- 

 pus, conjugate in pairs like the conidia of the Smut 

 fungus of corn, and produce zygospores, from zygos, a yoke, 

 in reference, we presume, to their supposed pairing. 

 The zygospores on germination are said to be capable of 

 penetrating, by their germinal filaments, the epidermis of 

 the plant invaded exactly after the manner of Peronospora. 

 The mycelium is said also to be only capable of effectually 

 growing when within the special host plants of the Proto- 

 myces. In this position only are the oogonia and oospores, 

 which at length bear the conjugating spores, produced. 

 This habit is also the same with that of Peronospora. The 

 so-called zygospores are minute transparent oscillating 

 bodies without cilia ; they are about the same in size with 

 (or perhaps a little smaller than) the zoospores produced 

 by the conidia of Peronospora nivea, Ung., as illustrated at 

 B, C, Fig. 112. True zoospores sometimes do not produce 

 cilia, and it is by no means uncommon to see zoospores 

 conjoined by a short band. The oospores burst and dis- 

 charge the little conjugating zygospores in spring, again 

 reminding one of the habit of Peronospora. Although we 

 are inclined to esteem the oospores of Protomyces as differ- 

 ent from the oospores of Peronospora nivea, Ung., yet there 

 is evidently room for a different opinion. New observa- 

 tions are needed. Prof, de Bary's paper, Beitrage zur 

 Morphologie und Physiologie der Pilze, was published in 

 1864. 



Peronospora nivea, Ung., produces resting-spores within 

 the stems and roots of the plants attacked (they occur in 

 company with the oospores of the Protomyces) ; therefore 

 all plants which have been attacked by these fungi should, 

 as far as possible, be burned. As both the Peronospora 

 and the Protomyces are peculiar to umbelliferous plants, 

 parsnips should not be grown a second year in the place 



