310 Mr. J. Ralfs on Spirulina and Coleocheete. 
of series of cells radiating from a centre and connected together 
by a hyaline substance ; spores imbedded in the frond*, 
1. C. scutata, Bréb. Cells having on their upper surface a cylin- 
drical truncate sheath, from which a bristle at length protrudes. 
Bréb. Ann. d. Sc. Nat. série 3. vol. i, p. 29. tab. 2. 
In ponds, parasitic on aquatic plants, especially on the under sur- 
face of the leaves of Potamogeton natans and Nymphea alba when 
verging to decay. Victoria Park, Manchester, and in Windermere, 
Mr. Sidebotham; Aberdeen, Dr. Dickie; Henfield and near Tun- 
bridge Wells, Sussex, Mr. Jenner; near Fleetwood, Mr. J. S. Ash- 
worth; near Bristol, Mr. Thwaites; ponds at Singleton and Sketty 
near Swansea, Mr. Moggridge ; also abundant in Cromlyn Bogs near 
the same town. In several stations near Penzance and Dolgelley. 
This parasite, I suspect, is not uncommon, but from its mi- 
nuteness it is difficult to detect, especially when growing on leaves 
which still remain slightly green. It was first gathered m this 
country by Mr. Sidebotham, who kindly sent me specimens ex- 
ceedingly well-mounted. 
The very minute fronds, which to the naked eye seem mere 
specks, are under the microscope found to consist of many series 
of cells radiating from a centre and connected together by a co- 
lourless substance, which is best seen at the margin. Hach series 
of cells is repeatedly dichotomous ; the cells are longer than broad 
and truncate, the four or five central ones somewhat irregular, 
the others of equal length, forming concentric circles. These 
circles vary from five to twenty in number. Endochrome green, 
and usually contracted into a central spot in each cell. 
After some time a cylindrical, colourless process appears on 
the upper surface of each cell; it is directed outwards and is trun- 
eate at the extremity; within it a bristle becomes visible, gra- 
dually protrudes, and finally becomes much elongated. The 
bristle sometimes contains pale granular matter, when it may be 
traced even before it issues from the tube. Before the protrusion 
of the bristle the sheath is always truncate, asif open at the end, 
but afterwards it is sometimes conical, as if a membrane was 
pushed out and then perforated. 
Although the fronds are closely appressed, if care be used they 
may generally be separated by a penknife from the leaf on which 
they grow. The margin of the frond is well-defined ; in young 
plants it is usually circular, but in the larger specimens often 
slightly lobed. 
The spores, which are imbedded in the frond, are suborbicular 
* «Frons disciformis, adpressa filamentis e centro radiantibus szpius 
coadunatis; formata filamenta articulata dichotomo-ramosa e dorso articulo- 
rum vaginas cylindricas, truncatas longe setigeras passim prodeunt, Endo- 
chromas viride.’—Bréb. Ann. d. Sc. Nat. série 8. vol. i. p. 29. 
