ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 343 



semi-cell, but in a few species the pyrenoids occur either in the angles 

 only or else in addition to those in the centre. S. brasiliense and 

 S. graude differ from most of the other species examined in their very 

 numerous pyrenoids. In S. grcmde also some individuals show a 

 tendency to the parietal disposition of the chloroplast by the total 

 disappearance of the axis in the centre of the semi-cell, leaving the 

 peripheral lobes of the chloroplast isolated. 



The second part of the paper discusses the behaviour of the chloro- 

 plasts durin.o- cell-division. Those of Xetrium and Cylindrocystis 

 probably behave much as do those of Closterium, as described by 

 Lutman. In all the Placoderm Desmids examined the process of cell- 

 division is rather different from that of the Saccodermae. The nucleus 

 of the cell completes its division, and the two new colourless semi-cells 

 can readily be distinguished before there are any visible changes in 

 the chromatophores. Tiie latter then ra23idly stream through the 

 isthmus from the old semi-cell into the new one, so that by the time it 

 is fully formed it is usually uniformly green. The process is completed 

 by the division of the chloroplasts at the isthmus of each individual. 

 In those species in which the points at which pyrenoids may occur are 

 fixed the young semi-cell is provided with a corresponding number of 

 pyrenoids by the budding of those already existing in the old semi-cell. 

 Where the pyrenoids are indefinite in number and scattered, a number 

 of these enter new semi-cells together with the budding chromatophore. 

 A striking feature of the ingrowth of the chloroplast in many species is 

 the rapidity with which the cell-wall of the young semi-cell is completely 

 mantled by the chloroplast, often at the expense of the more central 

 parts of the semi-cell. This phenomenon is responsible for the forma- 

 tion of parietal chloroplasts in isolated specimens of species which 

 normally possess axile ones, and probably also for their original produc- 

 tion in species in which they have been permanently acquired. A. G. 



Fresh-water Algae from Santo Paulo. — 0. Borge {Ark. Botanilc, 

 1919, 15, Xo. 13, 1-108, 8 pis.). The algse here recorded were 

 collected by Dr. Lof gren and sent to Prof. Nordstedt, who has published 

 a certain number of them in Wittrock and Nordstedt's " Exsiccatse." 

 Most of the Oedogoniacese have been published in Hirn's monograph. 

 The collection was afterwards handed over to the author for further 

 investigation, and the publication of figures. Nearly 400 species and 

 numerous varieties are enumerated ; and 27 new species and several 

 varieties are described in the present paper. E. S. G. 



Sub- Antarctic and Antarctic Marine Algse. III. Chlorophyceae. — 

 D. E. Hylmo (Wisseiisch. Ergebn. Sckicedisck. Sildpolarexped., 1901-3, 

 Band IV, hef. 16, Stockholm. 1919, 20 pp., 36 figs.). A report of the 

 marine Chlorophycese collected by Dr. Skottsberg on the coasts of 

 Tierra del Fuego, Graham's Land, S. Georgia, and the Falklands. To 

 each species is appended a list of synonymy and bibliography, 

 geographical distribution, and critical observations. Nineteen species are 

 included, one, Bryopsis magellanica, being new. E. S. G. 



