822 



SYSTEMATIC HISTOEY OF THE rN'FrSORlA. 



siicli habitats, but common in springs 

 and ponds generally. 



Mr. Ralls (op. cit. p. 852), however, 

 in part supports Ehrenberg, declaring 

 that, though identical with Conferva 

 ochracea (Uillwyn), yet "Ehrenberg is 

 no doubt correct in placing the plant in 

 this genus, as the filaments are silicious 

 and cylindi'ical." 



Nageli describes and figures a species 

 which he refers to the genus Gallionella ; 

 but it is a doubtful membigr. His de- 

 scription, however, especially that of the 

 self-division, induces us to give it nearly 

 in his own words, with his name (Ray 

 Society, 1846, p. 219). 



M. Ndqell (R.). — Shortlv cvlindi'ical ; 

 diam. •014'" to -027'". Marine!' Naples. 



"Both the terminal surfaces of the 

 cylinder are flattened ; so that, when seen 

 sideways, it appears rectangular, with 

 the angles rounded off. It is composed 

 of one simple cell, whose membrane is 

 covered by a siliceous plate; and its 

 cavity contains chlorophyll-gTanules, 

 which lie upon the membrane in two 

 circular bands, (xv. 26-28.) Each of 

 these bands occupies one of the obtuse 

 angles of the cylinder, and appears annu- 

 lar from above, rectilinear from the side. 



" In developing, the relative length of 

 the cylinder increasing, a septum divides 

 it into halves (xv. 28 c), which when 

 complete, the latter separate as two di- 

 stinct beings. The nascent chlorophyll- 

 granules are either spread equally over 

 the surface, or more frequently arranged 

 in radii from the nucleus in the centre ; 

 they lie in the com'se of the currents 

 streaming fi'om the nucleus. Compared 

 with a cell of Confer^'a, or of Spirogyra, 

 all three agree in the forming of a septum. 



in the similarity of their contents, and in 

 the depositions of extra-cellidar sub- 

 stance. But Gallionella ditfers fr-om 

 both, by the production of an individual 

 from every cell, also by the chlorophyll 

 forming two lateral bands, and the sili- 

 ceous extra-cellular substance an inter- 

 mediate one. 



" So far as my investigations go, 

 Gallionella, which, according to Ehren- 

 berg, possesses a bivalved or multivalved 

 shield, agrees with the above-described 

 plant in all essential particulars. The 

 lines, for instance, which would intimate 

 a division of the shell into two or more 

 pieces, are the septa by which the cell- 

 division is eflfected. As in the filiform 

 Algae, these walls at first appear as deli- 

 cate lines ; then, by an increase of thick- 

 ness, seem two clearly defined lines ; and 

 at last present themselves as two lamellae, 

 separated by an intermediate third line. 

 The perforations which Ehrenberg de- 

 scribed, I look upon as nothing more 

 than intercellular spaces, formed be- 

 tween the two new-formed cells and the 

 parent cell. These so-called perforations 

 are only visible, therefore, on the two 

 lateral borders where the wall abuts 

 upon the membrane. The Confervoid 

 AJgae exhibit a similar appearance." 



GallioiieUa (?) Novce HoUandice (Ehr.), 

 Avon River, Australia ; G. gibha (Ehr.), 

 fossil, Georgia; G. punctata (Ehr.), 

 Western Asia; G, tincta (Ehr.), Ural 

 Mountains ; G. gemmata (Ehr.), Siberia; 

 G. lineolata (Ehr.), fossil. North Asia; 

 G. undata (Ehr.), Himalaya Mountains ; 

 G. curvata (Ehr.), India; G. vaginata 

 (Ehr.), India; G. Nilotica (Ehr.), River 

 Nile, are species known to us only by 

 name. 



Genus ARTHROGYRA (Ehr.). — The characters of this genus are unknown 

 to us ; but, judging from Ehrenberg's figures of the species, it seems to have 

 been constituted for the reception of those forms of Melosfra which, like 31. 

 Dichieii, produce horizontal, elongated, tapering internal bodies or sporangia. 



Abthrogyba Guatimalensis, EM. pi. 

 33. 6. f. 1. Fem-earth. Guatemala. — 

 Filament straight, jointed, with crenated 



margin, 

 body. 



and straiofht, fusifonn internal 



A. semilunaris, EM. pi. 33. 6. f. 2. 



Guatemala. — Filament jointed, curved, 

 \^^th creriate margins, and semilimate 

 internal body. 



Genus DISCOSIRA (Rab.). — Frustules united into a short filament, with 

 a thick mucous covering ; in lateral view circular, having a uniformly punc- 

 tate centre, a border of numerous (24 to 33) slightly curved, oblique, ray- 

 like lines, and a marginal crown of teeth (50 to 64). 



DiscosniA sidcata (Rab.). — Frustules I rows, which con-espond to the teeth of 

 in front view with deep transverse fur- | the lateral surface. Rab D. p. 12, t. 3. In 



