(EDOGONIUM. 



[ 469 ] 



OIDIUM. 



and then germinate in this way in situ, the 

 root-like processes remaining engaged in the 

 parent-cell. Very often they attach them- 

 selves upon the parent filament to germinate. 

 The next stage after germination presents 

 two different classes of phenomena ; in the 

 one the young plant elongates gradually 

 into a jointed filament by extension and 

 cell-division; in the other the contents of 

 the unicellular or bicellular germinating 

 plant become converted into minute globular 

 bodies, which are discharged by an orifice 

 formed at the summit of the filament by a 

 circumscissile dehiscence of the cell-mem- 

 brane (PL 5. fig. 7 /, t). The after-history 

 of these globular bodies is not certainly 

 known; the function of spermatic bodies 

 has recently been attributed to them. We 

 have seen bodies of similar appearance pro- 

 duced in the ordinary cells of decaying fila- 

 ments (fig. 7 A). 



The (Edogonia likewise produce large 

 resting-spores (fig. 7 ff), which are formed 

 from the entire contents of the upper of the 

 two cells, developed as above described. It 

 is stated by Pringsheim that a slight rupture 

 of the parent-cell wall takes place at the 

 side during the development of the spore ; 

 from the small orifice thus formed a portion 

 of the nascent spore bulges out, afterwards 

 becoming retracted; and this author believes 

 that the bulging portion of the spore-mass 

 becomes fertilized through the agency of the 

 little globular bodies above alluded to as 

 produced by some of the germinating zoo- 

 spores. Ultimately the spore, while increa- 

 sing in size, retracts itself from the walls of 

 its parent-cell, and lies free in the cavity, 

 presenting a double coat, the outer of which 

 is thick and tough ; its contents acquire a 

 red colour as it ripens. The parent-cell of 

 the spore mostly acquires a globular or ellip- 

 tical form, appearing like a kind of nodule 

 on the filament ; and the ripe spore, of glo- 

 bular, elliptical, or depressed spherical form, 

 is mostly of greater diameter than the ordi- 

 nary cells. The ripe spore escapes by the 

 decomposition or dehiscence of the parent- 

 cell ; the history of its germination does not 

 appear to have been traced. 



The systematic arrangement of the (Edo- 

 gonia is at present in a very confused condi- 

 tion. Hassall and Kiitzing have enumerated 

 a number of species which rest on very in- 

 sufficient grounds, for the length of the 

 joints appears variable. The synonymy of 

 the more distinct forms is also perplexed. 

 We are compelled to content ourselves with 



selecting a limited number of species, which 

 present tolerably satisfactory characters. 



1. GE. vesicatum, Link. Filaments 1-2500 

 to 1-3000" in diameter, joints two to four 

 times as long as broad ; spore-cells globose, 

 swollen. [This appears to include (E. Rothii, 

 Candollii, and ochroleucum.'] 



2. (E. tumidulum, Kg. Filaments 1-1400 

 to 1-1800" in diameter, joints two to six 

 times as long ; spore-cells oval, swollen. 



3. (E. grande, Kg. Filaments 1-700 to 

 1-900" in diameter, joints one to four times 

 as long ; spore-cells elliptical, swollen. [Pro- 

 bably includes (E. giganteum, Ktz. and Vesi- 

 culifera lacustris, Hass.] 



4. CE. Landsborouahii, Hass. Filaments 

 1-500 to 1-700" in diameter, two to four 

 times as long; spore-cells roundish-oval, 

 swollen. 



5. (E.capillaceum,K%. Filaments 1-1 200" 

 long, one and a half to two times as long ; 

 spore-cells elliptic-globose, slightly swollen. 

 [Vesiculifera virescens, Hass.] 



6. (E. crispa, Vauch. (PI. 5. fig. 7 a). 

 Filaments 1-700 to 1-900" in diameter, 

 equally or twice as long ; spore-cells slightly 

 swollen, spores squarish. Filaments curled. 

 Apparently Vesiculifera princeps, Hass., 

 Conferva capillaris, Ag., Tiresias crispa, 

 Bory, &c. It seems to us also that Thuret's 

 (E. vesicatum (Ann. des Sc. not. 3 ser. xiv. 

 pi. 19) belongs here. 



BIBL. Link, Hor. physic, berolin. (1820); 

 Kiitzing, Sp. Alg. p. 364, Tab. Phyc. Bd.iii. 

 pi. 33, &c.; Hassall, Br. Fr. Ala. p. 195; 

 Thuret, Ann. d. Sc. nat. 3 ser. xiv. p. 226; 

 Pringsheim, Monatsber. Berl. AJcad. 1855, 

 Ban und Bildung der Pflanzenzelle, Berlin, 

 p. 33, 1854. 



OIDIUM, Link (Acrosporium and Sporo- 

 trichum, Greville, Torula, Corda). A sup- 

 posed genus of Mucedines (Hyphomycetous 

 Fungi), but very probably consisting merely 

 of imperfect conditions of plants of more 

 complex nature. The Oidia have recently 

 attracted great attention on account of the 

 extraordinary development of the form called 

 Oidium Tuckeri on the vines of Europe and 

 the Atlantic islands. This, however, like 

 O. leucoconium and others, appears to be 

 only the conidiferous mycelium of an ERY- 

 SIPHE or some allied plant; the particulars 

 of its history are given more at length under 

 VINE FUNGUS. Oidium lactis seems also 

 referable to Torula, or to the mycelium of 

 PENICILLIUM. O. abortifaciens, Lk. is an 

 imperfect state of CLAVICEPS; O. albi- 

 cans, C. Robin, the fungus of APHTHA, is 



