Miscellaneouft. 219 



Two new Oeneric Types of the FamHies SaprolegnicfC and 

 PeronosporcoD. By MM. E. IIoze and M. Coknu. 



Tho authors remark that it is questionable whether the Sapro- 

 Icgnieaj should be referred to the algic or the fungi. They think that 

 one of their new genera furnishes an argument in favour of tho 

 latter. It is an endophyte, parasitic upon tho smallest of our pha- 

 nerogams, IFo/^ Michelii, Schleid. (Lemna a rrhiza, Linn.), and pre- 

 sents some characters belonging both to tho Saprolegniea; and Pe- 

 rouosporea;, so that it may to a certain extent be regarded as inter- 

 mediate between the two families. They name it Cystosiphon 

 pythioides. 



Its mycelium, which traverses the cells of the Wolffia by perfo- 

 rating their walls, developes the two kinds of reproductive organs 

 (sexual and asexual) which have already been indicated in the 

 species of this family. The first mode of reproduction terminates in 

 the formation of an oospore, the thick epispore of which resembles 

 that of the oospores of the Peronosporea). This oospore originates 

 here, however, from the fertile union of the antheridian and oogonic 

 plasma, effected by means of a short process emitted by the antheri- 

 dium, which penetrates into the oogonial cavity. 



The so-called asexual reproduction of Cystoslplion is effected by 

 means of zoosporangia. These arc represented by vesicles which 

 terminate certain branches of the mycelium in peripheral cells of 

 the WolJJid. When mature, each of these vesicles, which is isolated 

 by a septum from the rest of the mycelium, emits a tube which runs 

 perpendicularly to meet the cellular wall separating it from the 

 water. This flattens itself against the cellulose membrane, which it 

 perforates by an oxosmotic action, and then grows out into the 

 water until its extremity becomes stationary and slightly thickened. 

 The plasma of the zoosporangium is then instantaneously diffused in 

 this extremity of the tube in the form of a jdastic spheroid, which in 

 a few minutes contracts and shows a very delicate enveloping mem- 

 brane continuous with the tube. The following phenomena are then 

 rapidly witnessed in the interior of this vesicle : — A network of clear 

 lines indicates the segmentation which takes place in the plasmic 

 mass, and the cilia appear ; the segments separate from each 

 other and constitute the zoospores ; these agitate their cilia, and 

 move more and more rapidly ; lastly a portion of the wall of the 

 vesicle becomes absorbed and tlio zoospores escape. Their move- 

 ments last for about half an liour : they then become spherical, 

 lose their ciUa, become clothed with a membrane, and germinate by 

 emitting a tube. This gcrniinativo tube then penetrates by perfora- 

 tion into the cells of healthy fronds of ITo/^, where it is developed 

 into a mycelium. 



The Peronosporea), to which the second new generic type belongs, 

 have hitherto included only the genera Cystnpus and Po-onos^wra. 

 The cndophytal fungus, parasitic on Eriyiron canadcnse, Linn., de- 

 scribed by the authors under tlie name of Bnsidiophora cntospora, 

 is distinguished at the first glance from the above genera by its 



