340 Mr. J. Ralfs on the Nostochinez. 
Aphanizomenon agrees in its filament with Oscillaturia, but is 
sufficiently separated by its conspicuous sporangia, which are si- 
milar to those of Dolichospermum. It differs from all the other 
genera in the Nostochinee by the absence of vesicular cells and by 
its obsoletely articulated filament. 
1, A. Flos-aque (Linn.). Filaments cohering laterally in flat lamellze 
which separate at their extremities into fasciculi; sporangia cylin- 
drical with an inconspicuous covering. Byssus farinacea virescens, 
aque inspersa, Linnzeus, Flora Lapponica, no. 532 (1737), ed. 2nd, 
p- 388 (Smith, 1792); Flora Suecica, ed. Ist, no. 1128. Byssus 
Flos-aque, Linn. Species Plantarum, no. 1168 (1753), ed. 2nd, 
p: 1637. Conferva Flos-aque, Roth, Catalecta Botanica, fasc. 3. 
p- 192 (1806). Oscillatoria Flos-aque, Agardh, Synopsis Alga- 
rum Scandinavie, p. 107 (1817) ; Syst. Algarum, p. 59. _Nostoe 
Flos-aque, Jiirgens, Algze aquaticze. Limnanthe Linnei, Kitzing 
in Linnea, vol. xvi. p. 86. Limnochlide Flos-aque, Kitzing, 
Phycologia Generalis, p.203 (1843) ; Phycologia Germanica, p. 168; 
Species Algarum, p. 286; Tabulee Phycologicee,t.91. fig.2a. dpha- 
mizomenon incurvum, Allman in lit. cum specimine. 
Probably not uncommon. Grand Canal Docks, Dublin, Professor 
Allman. 
Sweden, Linneus ; Germany, Kiitzing. 
I am indebted to Professor Allman for a beautiful and cha- 
racteristic specimen of this species. In its dried state the stra- 
tum appears to be composed of minute flocculi, and, with the 
exception of colour, might not unaptly be compared to scattered 
snow-flakes. The colour is opake, zruginous green, which how- 
ever becomes more or less altered after being dried a second 
time. The microscope shows that the flocculi consist of parallel 
filaments united together laterally, and forming a flat layer which 
appears plumose from the filaments converging at the ends into 
little conical or subulate tufts or pencils. The filaments are 
straight, obtuse, not attenuated ; the joints are rather longer than 
broad, faintly visible, and especially difficult of detection in con- 
sequence of their granular contents. Kiitzing describes the spo- 
rangia as elliptic. In the Dublin specimen they are few in number 
and immature ; but in specimens given me by Professor Kiitzing 
they are linear, much elongated, often ten or twelve times longer 
than broad, and resemble those of the next species except in 
having a far less conspicuous hyaline covering. The best di- 
stinctive mark between these species is the lateral coherence of 
the filaments in A. Flos-aque. 
In the dried state, the only condition. in which I have seen it, 
the Aphanizomenon Flos-aqua i is easily recognized by its floccu- 
lent appearance, even to the naked eye. I believe that not only 
was it one of the earliest-known plants in this group, but that it 
