ABCHEB OX PALMOGLCEA MACROCOCCA (KUTZ.). 17 



naturally distinguished generic types, and these indeed, so far as I can 

 see, are the only two alluded to by De Bary. These are — 



(4) Cylindrocystis (Menegh.), and — 



(5) Mesotsenium (Nag.). 



Both these, as previously indicated, agree with the foregoing (P. 

 Boemeriana excepted) as well as with each other, in the elongate and 

 elliptic or oblong form of the cells, but they are distinguished from them 

 and from each other by the structure of the cell-contents. In Cylin- 

 drocystis the cells possess granular chlorophyll-green contents, and at 

 the centre a paler or less dense region. This clear central space is de- 

 scribed by De Barjr, for C. Brebissonii, as rounded or four cornered ; to 

 me it appears as of extremely indefinite outline, if indeed it can with 

 propriety be said to possess a proper outline at all. "Within this occurs 

 a nucleus, but not always evidently. Beyond it, at each side, occurs 

 one, or in longer cells, about to divide, occur two somewhat elongate, 

 apparently dense bodies (starch' granules), from which radiate, in an 

 irregular sub- stellate manner, the general granular cell- contents. The 

 arrangement of the cell-contents here reminds one very much of that in 

 Zygnema. Reproduction is by conjugation, and evolution from the con- 

 tents of the spore, in germination, of four young cells the same as the 

 parent.* 



To this genus belongs clearly Palmoglcea Meneghinii (Kiitz.) = Pe- 

 nium Brebissonii (Ralfs) = Cylindrocystis Brebissonii (Menegh.), the last 

 being, doubtless, the correct appellation. And not less certainly, I 

 believe, does Trichodictyon ruprestre (Kiitz.) belong here. The species 

 so named by Kiitzing I believe to be identical with Cylindrocystis crassa 

 (De Bary) ; the remarkable mode of growth pointed out by De Baryf not 

 being constant, seems to decide that it is not of sufficient importance to 

 suggest the separation of this species from Cylindrocystis, seeing that 

 the internal structure seems to coincide. It is true, assuming that I 

 am right in my identification of this plant, that Kiitzing places it in a 

 genus by itself, distinct from his Palmoglcea ; bat the reasons for this 

 course are not founded on any essential peculiarities of the cells them- 

 selves, or their mode of growth, but upon external accidental circum- 

 stances, which, so far as I can see, are in no way connected with the 

 plant itself or its growth, and consequently erroneously introduced into 

 his conception and definition of his genus. To indicate the circum- 

 stances on which Kiitzing relies for his generic distinctions, I cannot 

 do better than repeat here his generic characters for Trichodictyon : \ — 

 "Phycoma amorphum gelatinosum; substantia gelinea matricalis locu- 

 loso-vesiculosa ; loculi fibris delicatulis reticulatim fasciculatis circnm- 

 texti celluliferi." It will be seen that Kiitzing relies here mainly for 

 his generic characters on the filaments accompanying the cells being in- 



* De Bary, op. cit., p. 37, t. vii. E., 18-22. 

 f Op. cit., p. 37, t. vii. C. 4-6, 9. 

 \ " Species Algarum," p. 230. 



