AECHEil — ON PALMOGLCEA MACROCOCCA (XUTZ.). 19 



then, either after the manner of C. Brebissonii, in a transverse direction, 

 causing the two new corpuscles to lie in the direction of the longitudinal 

 axis of the mother -cell, that is, perpendicular to the new septum, or the 

 subdivision of the central corpuscle of each half of the mother-cell may 

 apparently take place in a direction on a line with the longitudinal axis 

 of the mother-cell, causing, in this case, the two new corpuscles to lie 

 in a direction perpendicular to the original axis of the mother-cell, that 

 is, parallel to the new septum. Now, whichever of these cases holds 

 good, the elongation of each new cell seems to take place in the direc- 

 tion of a line connecting the two new central corpuscles, which always 

 thus lie in the direction of the longitudinal axis of every cell when about 

 to divide, which always, as before stated, takes place transversely, or in 

 the direction of the narrow diameter. Thus, in the former case, the 

 repetition of the process of cell-division does not alter the relative posi- 

 tions of the (so to speak) north and south poles of the generations of 

 cells, whilst in the latter case each alternate repetition of cell-division 

 changes the longitudinal axis of each generation from running north 

 and south to east and west, and vice versa, in the following generation ; 

 that is to say, each repetition of the process presents a division of the 

 cell-generations, according to two directions alternating with each other 

 at right angles. I do not imagine that these two modes of behaviour 

 possess any specific importance ; further observation may determine if 

 they have. The latter mode seems, so far as my experience goes, to be 

 the rarer ; whilst I fancy also the plants presenting it seem to be larger 

 usually than those which exhibit the former plan. The endochrome in 

 this plant is very dense and opaque, rendering it a matter of great dif- 

 ficulty to discern a nucleus, or the arrangements of the contents. It is 

 perfectly distinct as a species, and constant ; and the remarkable peculia- 

 rities of which I have endeavoured to convey an idea strikingly distin- 

 guish it from any of its allies. The plant is by no means uncommon 

 here, though Kutzing gives but one locality — the Black Forest. De 

 Bary does not say whether it is common or rare, but I should argue 

 from the context that it is as common with him as here. So much, in 

 passing, for the genus Cylindrocystis. 



I shall now advert to the last genus, Mesotsenium (Nag.). Plate I., 

 Pigs. 1 to 31. In this genus the structure of the cell-contents is dif- 

 ferent from any of the foregoing. Here there runs either directly 

 through the longitudinal axis of a cell, or sometimes slightly excentri- 

 cally, a more or less compressed, sharply-defined, dense " chlorophyll- 

 plate" (often, however, difficult to be detected, I believe, owing only 

 to being hidden by the remainder of the contents), whose margin either 

 touches the cell- wall, or leaves a more or less wide intervening space. 

 "When the remaining contents are not too dense and abundant to permit 

 its being readily perceived, this chlorophyll-plate, when its edge is to- 

 wards the observer, appears either, in some species, like a narrow vertical 

 axile green band, swollen at the middle at each side, and reaching entirely 

 from end to end of the cell — or, in others, as a somewhat lenticular body, 

 thus, in this edge view, presenting a fusiform outline, and not reaching 



