' W
II- i
í
A C H N A N T H E S ü n i p u n c t a t a .
Single-spotted Achnanthes.
frT'
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C l a s s a n d O b d e r CRYPTOGAMIA ALG/E, Linn N a t . O b d . ALGÆ, Juss.
G E N E R IC C H A R A C T E R .
Corpuscula plana, articulata, stipitata, vexillifonnia, articulis secedenlibus.
Plane, jointed, stipitate, standard-shaped minute bodies, separating at the
articulations.
S P E C I F IC C H A R A C T E R .
A c h n a n t h e s unipunctata ; arlicuUs perpaucis, quadraticis, margine transver-
sim striatis, puncto colorato nolatis.
A. joints very few, square, transversely striated at the margin, marked with
a coloured spot.
A c h n a n t h e s unipunctata, Carm. MSS.
D iatoma u n ip u n c ta tu m , Ag. Syst. Alg. p . 6.
F h a g i l l a r i a u n ip u n c ta t a , Lyngb. H yd . Dan. p . 183. t. 62.
Hab. Sea-shores, parasitic on various filiform Algæ. Appin, Captain C a r-
m ic h a e l .
Plant copiously diffused among the various capillary Algæ, and investing
their stems and branches ; to the naked eye appearing notliing more
than a minute green covering or pubescence. Filaments, i f such they
can be called, rectilinear, so much compressed as almost to be plane,
with very thin margins, the whole composed of 4 -6 joints, the lowest of
which is furnished with a stipes at one o f its angles ; jo in ts equal in
length and breadth, transversely striated, the striæ dense, reaching about
half-way from the margin on each side, towards the centre, which is
occupied bj' a circular spot of a rose or orange colour. The joints are
articulated to each other by the alternate angles, b u t fall asunder with
such facility, that it is difficult to obtain a view of them in situ. When
floating about in profusion after their separation. Captain Ca rm ic h a e l
observes that they become grouped together in a singular manner by a
sort of corpuscular attraction.
For a knowledge of the exact structure of this curious little
Alga, and of its existence on our shores, we are indebted to
Captain C a r m i c h a e l . A g a r d h and L y n g b y e did not
287