BRAUN, ON UNICELLULAR ALGJE. 95 



j3. Cambio', tlie unicellular individuals associated into a c(enohiiiM 



(pseudo-multicellular) ; Hydrodidyon ; 

 y. Symicobiee, associated into families (pseudo-multicellular): Sciadium: 



b. Ambiguous, i. e. forming gonidia by means of transitional generations, 

 and indicating the transition to the multicellular Algce : 



a. EremobieB, as above : Cystococcus, CJutmcium ; 



13. Canobice, as above : Pediastrum, Sceiiedesmus, Goniim, Pandorina, 

 Stephanosphipra, SynapMa. 



B. Oligocytiue^, the vital cycle limited to few cells ; ceils, two or three, 



heterogeneous. 



a. Bicellular ; Codium, Vaucheria {Saprolegnia, Aclilya) ; 



b. Tricellular : Pllobolus. 



C. PoLYCYTiDE^E, Or multicellular, the vital cycle including many cells : 



a. Hojiiosocytidea, cells (the vegetative at any rate) subsimilar : 



a. Schkocytide<f, cells more or less separate from each other (pseudo- 

 unicellular) : 

 * Chorlslobice, cells quite separate: Navlcida, Closterium, Pleurococcus, 



Chroococcus. 

 ** Synceeobio'., cells loosely connected by gelatinous envelopes, asso- 

 ciated into families : Hchizonemu, Hormospora, Pahwdadylon, 

 Palmella, Ilydrurus. 



ft. Synechocytidece, cells contiguous (the family of cells becoming a 

 continuous thallus) : Himantidium, De^mldlKm, Spirogyra, Oscil- 

 laria. 



b. Neierocytideie, cells obviously differing in nature : Nosioc, Cylindros'po- 



rum, liivulana, (Edogonium, BidbocIi(cte, &c. 



In this classification, tlie first section (A) alone contains 

 Algce, in tlie author's opinion, truly unicellular, although 

 Algce, unicellular according to Nageli's definition, are in- 

 cluded in sections A, B, and C, a, a and /3 (in part) . It need 

 scarcely be remarked, however, that all the sections in this 

 classification taken from single characters are merely artificial, 

 and do not correspond with families foiinded iipou a real and 

 intimate affinity. Nor, indeed, would it seem that all uni- 

 cellular AJg(B, in the stricter sense of the term, are of neces- 

 sity so closely allied as to be included in a single and peculiar 

 tribe; points, the discussion of which is reserved till the 

 description of each genus is given. 



Some observations remain to be made respecting the ter- 

 minology of the Alg(E. The vegetative substance of the 

 Alg<B, as regards the varieties of forms, has received various 

 appellations, but by Kiitzing it has been termed in general 

 phycoma, for which the author would substitute phytoma, a 



