*
i i
il
1
Hab. Bogs at Fisher’s Castle ; Waterdown Forest ; P iltdown
Common ; Cross in Hand, &c. : Mr. Jenner.
Dolgelly, Caermarthen, and Penzance : Mr. Ralfs.
High Beech : A. H. H. Aberdeen : Dr. Dickie.
The fronds when empty are found to be minutely punctate,
the puncta being arranged in longitudinal rows. I t
differs from Tetmemorus granulatus in its form altogether
and in its puncta arranged in longitudinal lines.
2 . T e tm em o r u s g r a n u l a t u s Ralfs.
Plate L X X X IX . Fig. 6.
Char. Frond six or seven times as long as broad, tapering
both in fro n t and lateral views, but slightlg constricted
in the centre. Segments rounded at the extremities
and terminating in a colourless, projecting, lip-like process,
punctated. Puncta arranged in diagonal lines.
Crannies in a row down the centre o f the frond.
Closterium granulatum Breb., in Menegh. Synop. Desmid.
p. 236. Tetmemorus granulatus Ilalfs, in Annals of
Nat. Hist., vol. xiv. p. 257. pi. viii. fig. 2. T. granulatus
Jenner, in Plora of Tunbridge Wells, p. 198.
Hah. Bogs at Fisher’s Castle ; Scrubbs, Colebrook Park,
Waterdown F o re st; Ashdown Forest, and Cross in
Hand : Mr. Jenner. Dolgelly and Penzance : Mr, Ralfs.
High Beech : A. H. H. Aberdeen : Dr. Dichie.
Tetmemorus granulatus differs from the preceding species
in several respects. In the form of the frond, which is altogether
different, being quadriform in T. Rrehissoni, and fusiform
in the present species, in the remarkable lip-like projection
of the extremities of the segments, and in the arrangement
of the puncta in diagonal and not longitudinal lines.
Near the junction of the segments the puncta are observed
to be arranged in three or four transverse lines.
This species has been found by Mr. Ilalfs in a state of
conjugation, and with the sporangium formed similar to that
of numerous Closteria, and not differing from that of Staurocarpus
amongst the Conjugated. The steps of the formation
of this in Closterium and Tetmemorus are as follow.
Two fronds coalesce, a cell is gradually formed between
them into which the endochrome passes from each frond
and which finally becomes moulded into a distinct organ or
sporangium invested with its membrane.
61. E U A S T E U M Ehr.
Char. Frond compressed, deeply divided into two segments.
Segments longer than broad, usually pyramidal, emarginate'
at their extremities, and lohed and tuberculated or
sinuated.
Derivation. From zv, beautiful, and acrrpov, a star.
“ In this genus Ehrenherg includes Micrasterias Ag. (not
Micrasterias E h r.) and Cosmarium; Meneghini separates the
former from it, but includes it in the latter genus. Euastrum
appears to me to be distinct from both, and especially from
Cosmarium. I t agrees with Micrasterias in having lobes and
emarginate ends ; but the fronds are not incised, nor do the
lobes radiate from the centre. From Cosmarium it differs in
the lobed and emarginate segments, and also in the infiated
projections on the surface. These characters will also distinguish
it from the other geneia of this family.”— Ralfs.*
a. Segments o f the fro n d deeply lobed, tuberculated. Terminal
lobes cuneate.
1. E u a s t r u m v e r r u c o s um Ehr.
P la te X C I. Fig. 7.
Char. Frond denticulated. Segments three-lohed. Lobes
broad, subcuneate, with a broad shallow notch between each
lobe.
Euastrum verrucosum, Abhand. der Akademie d. Wissensch.
* Annals, vol. xiv. p. 188,