OF THE MELOSIEE^. 



821 



mode of development^ in the formation 

 of sporangia, stands alone and imsup- 

 ported — a serious difficulty in tlie way 

 of admitting Mr. Thwaites's conclu- 

 sions." For this and other reasons, he 

 was disposed to refer the process to the 

 development of internal cells, as in Meri- 

 dion, Himantidium, Odontidium, and 

 Achnanthes, and recorded his impression 

 that the process was not connected Avith 

 the sporangia. 



M. temds (K.). — Very slender; joints 

 cylindrical, smooth, longer than broad, 

 closelv connected, produced at their 

 jimction. KB. p. 54, pi. 2. f. 2. In the 

 polishino- powder of Limeberg. Diani. 

 1-5760".'^ 



M. Garganwa (Rab.). — Very slender ; 

 joints two or three times as long as 

 broad, with stout, protuberant, indi- 

 stinctly dentate junctions; disc flat, 

 punctated on the periphery. Rab D. p. 

 14, t 2. f. 8. Italy. After burning, it 

 reminds one of M. tenuis. 



Doiihtfid and imperfectly described 

 Species. 



M. Do:iyana (Van den Bosch). — Joints 

 cylindrical, finely punctated; length 

 equal to or a little longer than the 

 breadth. KSA. p. 29. Stagnant water. 

 HoUand. Diani. 1-1152" to 1-770". 



M. circularis. — GaUionella circidaris. 

 EM. pi. 35 A. 9. f. 3. Asia and America. 

 Filaments slender, curved ; joints broader 

 than long, closely connected, smooth, 

 with a single sutural line. 



M. Gallica. = GaUionella Gallica, EM. 

 pi. 9. 2. f. 2. Fossil. France, The 

 frustule has one diameter twice as long 

 as the other, and no suture or string. 



M. halophila = GaUionella hahphila, 

 EM. pi. 37. 5. f. 1. Em-ope. Frustules 

 minute, smooth. 



M. tcBniata— GaUionella tceniata, EM. 

 pi. 39. 3. f. 65. Atmospheric dust. The 

 figm'e shows a single subquadrate frus- 

 tule, wdthout any distinguishing cha- 

 racter. 



M. trachealis = GaUionella trachealis, 

 EM. pi. 8. 2. f. 18. Hungary. Ehren- 

 berg's figure is too imperfect to be in- 

 telligible. 



M. laminaris = GaUionella laminaris, 

 EM. pi. 39. 3. f. 64. Asia.^ The imper- 

 fect figure shows striated junction-mar- 

 gins. 



M. Scala = GaUionella Scaki, EM. pi. 

 8. 1. f. 24. Hungary. The figure re- 

 presents a slender continuous filament, 

 di^dded into smooth quadrate joints. 



M. ? mesodon = GaUionella ? mesodon 



{Fragilaria mesodon Y), EM, pi. 11. f. 10. 

 Bohemia. Filament slender, conti- 

 nuous, with smooth subquadrate joints, 

 having two puncta at each outer margin, 

 as in Fragilaria. 



M. ocliracea. = GaUionella ferrwjinea 

 (Ralfs). — Slender, oval, convex at both 

 ends ; smooth. In many, perhaps in all 

 chalybeate waters, and also in peat- 

 water, which contains a small proportion 

 of iron, this is to be foimd ; it is of the 

 colour of iron-rust, and in mineral 

 springs, in which it abounds, is often 

 taken for precipitated oxide of iron. It 

 covers everything under water, but 

 forms so delicate and floccose a mass, 

 that the least motion dissipates it. In 

 the spring of the year, this mass is com- 

 posed of very delicate pale-yellow glo- 

 bules, which can be easily separated 

 from each other. They unite together 

 in rows, like short chains, and produce 

 an irregular gelatinous felt or floccose 

 substance. About summer, or in autumn, 

 they become developed into more evi- 

 dently articulated and stilF threads, of a 

 somewhat larger diameter, but still form 

 a complicated mass or w^eb, and, either 

 from adhering to each other or to deli- 

 cate Confervfe, appear branched ; in the 

 young condition, when examined imder 

 shallow magnifiers, they resemble gela- 

 tine ; but with a power of 300 diameters, 

 the flexible granules are discoverable, 

 and, with dexterous management, the 

 little chains fomiing the felt or floccose 

 web can be made out. In summer, on 

 the other hand, its structm-e can be ob- 

 served much more easily and distinctly. 

 Early in spring, the colour is that of a 

 pale yellow ochre ; but in summer, that 

 of an intense rusty red. Diam. 1-1200". 



According to Kiitzing, this is not a 

 species of GaUionella, but a ConfeiTa; 

 it has no true silicious lorica, as have 

 true Diatomese ; and the coating of oxide 

 of iron is not an essential element, but 

 merely an incrustation, such as will form 

 on well-knoAvai Confervas placed imder 

 like circumstances, /. e. in water holding- 

 salts of iron in solution, which are sub- 

 sequently precipitated by exposure to 

 the air, and converted into the red oxide. 



The same author dift'ers from Ehren- 

 berg as to the part played by the so- 

 called GaUionella ferrurjinea in the pro- 

 duction of the oxide of iron in chalybeate 

 waters, of bog-iron ore, of clay-iron ochre, 

 &c. For, he observes, in many springs 

 rich in iron no such organism is foimd, 

 although other Confervce may be present 

 — Conferva^, however, not pecidiar to 



