Mr. J. Ralfs on the Nostochinee. 309 
numerous, very minute. Vesicular cells oval. Sporangia (two 
to eight in each chain) at first similar to the ordinary cells, but 
usually less orbicular ; finally they become more or less oval, the 
shorter ones approaching to orbicular, and the longer ones to 
oblong ; they are frequently but little broader than the vesicular 
cell ; in fact their size never differs so much as in many species. 
Cylindrospermum catenatum differs froma every other species in 
its numerous sporangia. 
Cylindrospermum contains many other species, several of them 
by no means uncommon in this country; but their descriptions 
must be deferred to some future period, as my friend Mr. Thwaites, 
who had paid great attention to them, was prevented by his ap- 
pointment at Ceylon from fulfilling his kind promise to describe 
them for this paper. 
PuLate VIII. fig. 14. a, immature filament; >, mature state. 
APHANIZOMENON, Morren. 
Filaments simple, flaccid, obsoletely jointed, “ cohering laterally 
into flat lamelle,” aggregated into a mucous stratum ; vesicular 
cells none ; sporangia linear, interstitial. 
(Aphanizomenon, Morren. Limnochlide, Kiitz.) 
Aphanizomenon forms a thin, tender, mucous stratum of a 
bluish colour. The filaments are extremely slender, flaccid, and 
very obscurely joimted. No vesicular cells have been detected. 
The sporangia are much elongated, either scattered or, more 
usually, solitary near the centre of the filament. 
I have examined an authentic specimen of Limnochlide Flos- 
aque, and as there seems to be no essential difference between 
Aphanizomenon and Limnochlide I have united them, retaining 
the former appellation on account of its priority. The filaments 
in both genera are described as cohering in flat lamellee, but that 
character is sometimes so little obviqus in dried specimens, that 
I am not inclined to place much dependence upon it as a generic 
distinction, especially as I could not detect it in recent specimens 
of a plant, presently to be described, which I think should by no 
means be placed in a different genus. 
Authors differ widely respecting the proper situation of this 
genus. In Harvey’s ‘ Manual of British Algze’ it is placed at 
the end of the Confervee, Montagne appends it to the Oscilla- 
toriee, Endlicher omits it altogether, and Kiitzing instituted for 
it a distinct family, which he placed between Leptotrichee and 
Nostochinee. Mr. Hassall, I believe, first placed it in this family, 
and I fully concur with his observation that “the true position 
of the genus is undoubtedly amongst the Nostochinee, connecting 
them with the Oscillatoriee.” 
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