Ij M
n f-.
t)■: t■
9. E u a s t r um s p in o s um Balfs.
Plate X C I. Fig. 9.
Char. Frond minute, somewhat oval, compressed, rather better
than tioice as long as broad. Segments twice emarginate
at the side. Angles often spinous, especially the distal
ones.
Euastrum spinosum YaMs, in Annals, vol. xiv. p. 192. pi.
vii. fig. 6. ; Jenner, Flor. Tunbridge Wells, p. 198.
Hab. Cheshunt: A . H. H. Barmouth: Rev. T. Salwey.
Mayfield ; Busthall Common ; Piltdown Common ;
Chiltington Common ; and Rackham, near Pulborough ;
Dolgelly ; Penzance : Mr. Ralfs.
A distinct though variable little species, and one by no
means uncommon.
10. E u a s t r u m b in a l e Ralfs.
Plate X C I. Figs. 4, 5.
Char. Frond about twice as long as hroad. Segments concave
or truncate, at the end not projecting beyond the acute
angles.
a “ Segments inflated at the hase, the notch hroad, forming
a concavity between the angles.”
fl truncatum. — “ Yronds quadrilateral ; the end truncate,
acute at the angles, with a small triangular notch in
the middle ; ” segments laterally twice crenate.
Heterocarpella binalis Turp.,‘ Kützing, Synops. Diatom, p.
70. Cosmarium binale Menegh., Syn. Desmid. p. 221.;
Ralfs, in loc. cit. ; Jenner, in loc. cit., p. 198.
Hab. Mayfield ; Piltdown Common, and bog near Cross
in Hand : Mr. Jenner. Dolgelly ; Penzance ; Mr.
Ralfs.
The variety fl may prove to be distinct.
385
62. MICRASTERIAS Ag.
Char. Frond compressed, deeply divided into two segments.
Segments lohed, radiant, and incised.
Derivation. From goKpos, small, and acrrspias, starred.
The flat and orbicular fronds, and the radiant and incised
lobes, will distinguish this at once from all other genera of
Desmideæ.
The genus Micrasterias of Agardh differs entirely from the
Micrasterias of Ehrenherg, which has been referred to the
Pediasti'um of Meyen.
1. M ic ra st er ia s rotata Ag.
Plate XC. Fig. 1.
Char. Fronds smooth, orbicular, ten-lobed. Lobes cuneate,
approximate, the end lobe emarginate, the others bifid, the
divisions being notched.
Micrasterias rota Menegh., Synops. Desmid. in Linnæa,
1840, p. 215. Echinella rotata Grev., in Hook. Br.
Flora, vol. ii. p. 398. (1830). Eutomia roZate Harv., Br.
Alg. p. 187. Euastrum rota Ehr., Infus. p. 167. tab. 12.
% . 1.; Pritch. Infus. p. 195. figs. 121—123.; Bailey,
American Bacillaria, pi. i. fig. 22. and fig. 24. Micrasterias
Ag., Bot. Zeit. 1827. ? Cosmarium stellinum et
C. truncatum Corda, Almanac de Carlsbad, 1835, p. 206.
pi. ii. pp. 22, 23. ; Ralfs, in Annals, vol. xiv. ; Jenner, in
loc. cit. p. 198.
Hah. Frequent in Sussex : Mr. Jenner. Henfield : Mr.
Borrer. About Barmouth : Rev. T. Salwey. Aberdeen
: Dr. Dickie. Stevenston, Ayrshire : Rev. D.
I.andshorougk. Penzance ; Dolgelly ; &c. : Mr. Ralfs.
Cheshunt Common : A . H. H.
The frond of this species in its young condition differs so
much from the adult form that it might be easily regarded as
a distinct production, the lobes being neither bifid nor dentated.
c c