Meloseira.] ALG/E DIATOM ACEA',. 401 



I. S. rupestris, Ag. (Rock Scythymmia). Ay. Syst. Ahj. p. 30. 

 — Viva rupestris, E. Bot. £. 2194 (not characteristic). 



" On the nearly upright face of a rock, bathed with a perpetual 

 trickling rill, at some distance above Fyloge bridge, near Hafod," Sir 

 J. E. Smith. — " 2 — 3 feet wide, spreading like a piece of very wet 

 leather." — In a dry state, in which only, of course, I have seen it, this 

 curious production strongly resembles a piece of thickish light-brown 

 leather. The upper surface is very prettily reticulated with raised irre- 

 gularly anastomosing veins, which form areolae from 1 to 3 lines in dia- 

 meter. Under the microscope it is found on dissection to consist of 

 densely packed very slender byssoid fibres, intermixed with minute 

 granules. 



Div. IV. DIATOMACEiE.' 



Granules (frustula) of various forms, plane or compressed, more 

 or less hyaline or transparent, rigid and fragile, in parallel series 

 or circles, free, naked, or imbedded in a mucous mass or gelatinous 

 frond, at length s-parating into definite segments. — Small, often very 

 minute plants, in the sea or in fresh-water, mostly parasitic or 

 forming floating masses, or mixed with other aquatic vegetables. 



Tribe XXII. Desmidie^e. 



Filaments cylindrical or angular, at length separating into seg- 

 ments (frustula). 



98. Meloseira. Ag. Meloseira. 



Frustula forming simple pseudo-articulated filaments, con- 

 stricted at the articulations, fragile, easily separating. — Name; 

 /x-/.o-, a membrane, and tope, a chain; in reference to the form of 

 the filaments. 



1. M. nummuloides, Grev. (ovaljointcd Meloseira); filaments 

 fragile* the joints scarcely BO long as broad at length converted 

 into ;. fterta of oval globules. Grer. M SS.,not of ' Agurdh. — 

 M. disct'gera, Ag, Syst. Alg. p. 8. — FragUaria nvmmulokUs, 

 fjgngb. Hydroph. Dan. p. 184./. 68 ? — Conferva nummuloidu, 

 DiOw. Conf.p. 4.V t. 11. 



Streams. Anion- the leaves of water-plants, in the river Lea at Wal- 

 thamstow, Mr, lhllwyn. — The name of nummulo'hUs should be retained 



for the present species, Duiwyn having the priority of other authors. 

 This arrangement is the more necessary, since Agardn is not at all cer- 

 tain about the plant Bubseoue&tlv published under the same name in 



2. M. llnrnri. (iivv. (Mr. l!,,rnrs M,lus,n;<); tilam.-iiN 

 very fragile, (fee joints rather longer than hroad at length OOtt- 



i Hv Dr. Ortrflk. 



8 i) 



