L'S
rarely constricted; striæ moniliform, 20 in -OOl". Lengtli o ffru stule
-0006" to -0028". Stipes never e.vceediug the length of the
frustule, solitary or subgregarious. v.v.
P- P>- 2S5. Grey. B. F.
W tf 4 'i 2- Prit. Anim. iv. I99-2Ü2.
dTV (P p I- ®P“ ™- J™"- I***'’™.
authen TT™V L Lyng- Tent. Ixx. B, ad specim.
authen. “ Herb. Grev. Achnanthes salina, Kütz. Bacill. xx. 5 . et
Bre-Mssom ®P“ ™' 'ï"® “™-
Be!îb7’T V T " V ’T ''- of Sussex, frequent. Pevensey, Sept. 1850.
f sw r ’ ^tP"'-= Bexhill, Oct.; and Newbav», Dec.
iXI u-t Pancing, July 1843, Mr. Jenner. Torbay, Mrs. Griffiths
(Mediterranean near Marseilles, and near Montpellier, May 1854, W. i n . ) '
An original specimen of Lyngbye’s in the Herbarium of Dr. Greville enables
me to refer this species to Echinella stipitata, while the specimens received
from M. De Brefoisson satisfy me that A. salina and A. intermedia of the
Bacillanen are also identical with the present. Some confusion appears to
have arisen from the fact that this species at one time forms a long fifoment,
and at another presents itself only in very short standard-shaped fronds • no
distinction m the form or structure of the valve is however to be dete’cted
between the two, and the varieties, if such they may be called, are often found
intermixed in the same gathering. Mr. Ralfs observes that “ the lateral view
IS more frequently constricted than in A. longipes,” but my own observation
fails to confirm this. Usually the S. V. appears almost linear, becoming
rapidly attenuated towards the somewhat acute ends, and not unfrequently
the valve is inflated at the centre, assuming an oval outline, with the extremities
slightly produced : a slight constrietiou is no doubt occasionally to be
Ï r Ï Ï ’ “ exception rather than
Plate XXXVII. 301. Forming a long filament, Plate XXXVII. 301 ft.
3. Achnanthes su bsessilis, Kiitz. Filaments offew frustules, rarely
exceeding 4 ; valve elliptical, extremities rounded; striæ moniliform,
24 m -001". Length of frustule -0013" to -0021". Stipes
very short, solitary, v.v.
Kütz^acill XX 4 Raben Süssw. Diat. viii. 3 . Ehr. Inf. xx. 3. Ralfs in
Ann. vol. 13. pi. xiv. 10. ad specim. authen. in Herb. Jenn.
DnrJ. (neville. Pilling Marsh, Lancashire Auc wTr.> jS,fym, . Scwotrl aind
Mr. Ralfs ; communicated by Mr. JeXer
Undoubtedly distinct from the last, with which it has sometimes been eonfounded.
Its distinctive characters are an abbreviated stipes, which generally
assumes the form of a mere cushion, and never reaches half the length of the
frustule, and elliptical valves with rounded, and not attenuate, extremities. It
is a much rarer plant than either of the former; or, being more inconspicuous,
has been more frequently overlooked. A remarkable instance of
tlie abnorra.al development adverted to under Meridion circulare has presented
itself in the present species, an example of which is figured in Plate XXXVIII.
302*. Here, the formation of a cell interior to the original one has proceeded
tlirough several successive stages, and the result is a compound frustule, consisting
of the mother-cell and a number of included cells, each successive
development being embraced by the others previously formed.
Plate XXXVII. 302.
4. Achnanthes e x ilis, Kiitz. Filaments from 2 to 50 frustules ;
V. linear-lanceolate, with obtuse extremities, occasionally somewhat
produced; striæ very faint. Length of frustule -0006" to
•0018". Stipes very variable in length, subgregarious or solitary.
Kütz. Bacill. xxi. 4. ad specim. quæ dedit am. De Brébisson. Ralfs, Ann.
vol. ]3. pi. xiv. 12. ad specim. quæ dedit cl. Auctor. Hass. Alg. c. 5.
Raben. Süssw. Diat. viii. 1. Achnanthes minutissima, Ralfs, Ann. I. c.
fig. II. Hass. Alg. I. c. fig. 4. ad specim. authen. in Herb. Jenn.
Fresh water. Near Lewes, Sept. 1852, March 1853. Parasitic on the
stipes of Gomphonema geminatum, Galway, July 1853 ; and Grassmere, Aug.
1853, W.Sm. Parasitic on the stipes of Gomphonema namculoides in the
tank of the Victoria regia, Edinburgh Botanic Gardens, Sept. 1853, Dr.
Greville. Monkland Canal near Glasgow, Oct. 1853. Mr.R.Hennedy. Saltcoats,
Ayrshire, Jan. 1854, Dr. Arnott. On Gomphonema geminatum, Dolgelly,
Mr. Ralfs. Wray, Lancashire, July 1850, Mr. Geo. Smith. Cheshunt,
Mr. Hassall-, communicated h-y Mr. Jenner. (Well near Marseilles, May
1854, W.Sm.)
1 am unable to find constant characters in the numerous British specimens
in my possession by which to constitute two species of the above, and feel
constrained to regard A. minutissima of Ralfs as a mere state or variety of the
present plant. It will be seen, by a reference to the figures given by Mr.
West, how sportive in habit of growth and length of filament are the
specimens with which I furnished him, and yet each extreme may not unfrequently
be found in close neighbourhood on the plant which serves as their
support.
The length of the stipes, upon which Mr. Ralfs seems mainly to rely, I
cannot accept as a specific character in the present species, as it seems to me
to be chiefly dependent upon the stage of growth. Thus Mr. Ralfs says, that
in A. minutissima “ the stipes is not longer than the frustule,” while in
A. exilis “ the stipes exceeds tlie frustule in length.” Now, in tlie specimens