ERYTHRJEUS. 



[ 245 ] 



EUASTRUM. 



willows. E. bicornis, Lk., occurring upon 

 maples, &c., has eight spores. 



Calocladia. E. penicillata, occurring onFz- 

 burnum Opulus, &c. The ultimate branches 

 of the appendicles are turned up, and the 

 four asci contain each eight spores; the 

 appendicles are thick upward from the base. 

 Perhaps part of the E. penicillata of the 

 Brit. FL belongs to C. berberidis and gros- 

 sularice, Lev., which have the terminal 

 branches of the appendicles straight and 

 cylindrical. Both have many-spored asci, 

 but in the latter the appendicles are rectan- 

 gularly dichotomous and bidentate, while in 

 the former they are twice or thrice dichoto- 

 mous and obtuse. 



Erysiphe. E. Pisi, Grev. is E. Martii of 

 Leveille, distinguished by its globose, many- 

 spored asci and the hyaline appendicles. E. 

 tortilis, Lk. has coloured appendicles ten or 

 more times the length of the conceptacle. It 

 grows on Cornus sanguinea, the Dogwood 

 tree. E. communis, Lev., is not very well 

 characterized ; it has coloured appendicles, 

 which are only twice or thrice as long as the 

 conceptacle ; the asci vary from four to eight, 

 as do also the spores contained in each. 

 This species grows on a great variety of her- 

 baceous plants, Ranunculacese, Composite, 

 Leguminosa3, Cruciferee, Polygonacese, &c. 



Perhaps a doubt might be admitted whe- 

 ther the above subdivisions really represent 

 more than six species of this genus. 



BIBL. Leveille, Ann. d. Sc. not. 3 ser. xv. 

 p. 109. pi. 6-11; Berk, in Hook, Brit. Flora, 

 11. pt. 2. p. 325, Trans. Hort. Soc. London, 

 ix. p. 61 ; Greville, Sc. Crypt. FL pi. 134, 

 164. figs. 2. 296; Tulasne, Comptes Rendus, 

 Oct. 17, 1853. See also OIDIUM. 



ERYTHRJ2US, Duges. See ANYSTIS. 

 Under that head we omitted the characters 

 of A. ruricola, }Heyd..,Eryth. ruricola, Duges 

 (PL 41. fig. 4 ; PI. 2. fig. 3 ; a, palp ; b, man- 

 dible), which is probably not uncommon. 

 They are : Body depressed, nearly oval, but 

 slightly emarginate at the sides, and some- 

 what broader behind than before; a few 

 hairs scattered over the surface ; eyes two, 

 black, placed at the anterior obtuse angles of 

 the body ; colour bright carmine, sometimes 

 blackish in the middle, paler along the back 

 and in front ; legs and palpi colourless, ex- 

 cept a bright red spot on each of the joints 

 at a little distance from the body. 



EUACTIS, Kiitz. A genus of Oscillato- 

 riacese (Confervoid Alg), of the tribe Rivu- 

 larieae, consisting of little, hard, solid, elastic, 

 mostly hemispherical bodies, from 1-2 to 2'" 



in diameter, growing upon stones in the sea 

 or rivers, &c. ; concentrically zoned, com- 

 posed of radiating, flagelliform, repeatedly 

 sheathed filaments, the sheaths of which are 

 open and slit above (PI. 4. fig. 16), but con- 

 nected together side by side, so as to form a 

 tough gelatinous mass, not becoming en- 

 crusted with carbonate of lime. To this 

 genus Kiitzing refers Rivularia plicata, atra, 

 and perhaps applanata of Harvey. These 

 plants are interesting on account of the 

 fibrous decomposition of the gelatinous 

 sheaths. 



BIBL. Harvey, Brit. Mar. Alg. p. 222. 

 pi. 26 A. (Rivularia) ; Kiitzing, Sp. Alg. 

 p. 339, Tab. Phyc. cent. ii. pi. 74-82. 



EUASTRUM, Ehr. A genus of Desmi- 

 diacese. 



Char. Cells single, compressed, deeply 

 divided into two segments, which are gene- 

 rally pyramidal and furnished with circular 

 protuberances, lobed or sinuated at the mar- 

 gins, and emarginate at the ends. 



Mr. Ralfs describes twenty-one British 

 species, of which the following are the most 

 common. 



* Segments deeply lobed; end lobe distinct, 

 cuneate, partly included in a notch be- 

 tween the lateral lobes. 



E. verrucosum (PI. 10. fig. 14). Rough ; 

 segments three-lobed, lobes broadly cuneate, 

 with a shallow notch; length 1-267". 



E. oblongum (PI. 1 0.fig. 15). Smooth, ob- 

 long; segments five-lobed; lobes cuneate, 

 emarginate ; length 1-156". 



E. crassum. Smooth; segments three- 

 lobed, subquadrilateral ; end lobe cuneate; 

 length 1-190 to 1-130". 

 ** Segments sinuated ; end lobe exserted 

 and united with the basal portion by a 

 distinct neck. 



E. didelta (PI. 10. fig. 16 ; 17, empty cell). 

 Segments with inflated base, intermediate 

 tubercles, and notched and scarcely dilated 

 ends ; side view, four shallow lateral lobes, 

 and one at each end; length 1-185". 



*** End lobe indistinct; frequently a process 

 or acute angle at the corners of the ter- 

 minal portion. 



E. elegans. Oblong; ends emarginate* 

 pouting, and rounded; length 1-890 to 



Conjugation has been observed in several 

 species; the sporangia are spherical, with 

 conical tubercles, or acute or obtuse spines. 



BIBL. Ralfs, Brit. Desmid. p. 78. 



