it is slightly different from those of Greville and Lyngbye.
It does not, however, differ so much as the varieties /3 and 7
of Kutzing. It is indeed clear from the individuals represented,
which occurred on the same frond of Porphyra, that
it is very variable. Achnanthes multiarticulata of Agardh,
gathered at Venice, is probably a mere variety. The number
of frustules in A. brevipes is by no means confined to
two or three, as Agardh’s specific character would intimate:
Greville figures five, and Lyngbye speaks of six. Neither is
any dependence to be placed on thecrenulation of the outer
border, which is quite obsolete in Dr. Greville’s plant.—
M. J. B.
a. A group of Achnanthes brevipes on Porphyra vulgaris,
magnified ; b. a frond, highly magnified.
2842. (Fig. 2.)
GDONTELLA aurita.
Woolpack Diatoma.
CRYPTOGAMIA Alga Diatomacem.
Gen. Char. Frustules adhering alternately by the
tooth-like angles, and forming a thread.
Spec. Char.................
Syn. Odontella aurita, Agardh Consp. Crit. Diat.
56.
Diatoma auritum, Lyngb. Hyd. Dan. 182. t. 62.
Ag. Syst. 6. FI. Dan. t. 1957. Hook. Engl.
FI. v. 5. Pt. 1. 404. Kutzing in Linn. v. 8. 585.
O n va'rious Algae, In the Frith of Forth, Dr. Greville ;
Spring: at Margate, Rev. M.J. Berkeley; Winter. Golden
yellow. Fronds consisting of a few oblong or nearly square
frustules, adhering alternately by the auricular angles.
Between the angles is a little convex projection. The
transverse diameter, which is generally the least, is occupied
by an oblong raised disk, which is only to be seen under
high powers of the microscope. Each frustule contains a
number of elliptic granules, which are at first disposed in
rows, but soon become scattered. It is well observed in
the English Flora, thatthe auricular angles give to the frustules
the appearance of microscopic woolpacks.—M. J. B.