ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 225 



Bot., 1920, 58, G5-9). A discussion of the distinguishing characters 

 of the genus Roija by which it can he separated from Glosterlum. These 

 are mainly two : — (1) The simple structureless nature of the cell- wall ; 

 and (2) the fact that division of the chloroplast into halves is delayed 

 until the cell has reached mature age, or even until it is about to divide. 

 A modified Latin description of Roya is given, and the new species 

 R. anglica is described. The latter was gathered near Birmingham in 

 the spring of 1916 in very shallow water, and has never been found in 

 such abundance again. It was almost a pure growth, affording numerous 

 cases of conjugation and thousands of zygospores. A. G. 



Studies on the Chloroplasts of Desmids. III. — X. The Chloro- 

 plasts of Cosmarium.— Xellie Carter {Ann. of Bot., 1920, 84, 

 265-85, 4 pis. and figs.). An illustrated account of the chloroplasts 

 found in Cosmarium. In most species these are axile, in a few they are 

 parietal. In the former either one or two chloroplasts occur in each 

 semi-cell, and very often in the axis of each chloroplast there is typically 

 one pyrenoid ; the actual number of pyrenoids depends on the individual. 

 Many of the smaller species have a single chloroplast in each semi-cell 

 consisting of a central axis, containing typically one pjrrenoid from which 

 radiate either four more or less forked plates or a number of simple 

 ridges or string-like outgrowths. In C. dijolosporum there is a rough 

 kind of parietal network arising from the lateral expansion of the ends 

 of the chloroplast rays extending from the central axis, [n C. pseudo- 

 pyramidatiun the plates arising from the central axis containing the 

 central pyrenoid or group of pyrenoids are very complicated in form 

 and irregular in arrangement. C. pyramidatum differs from the previous 

 species in having a more delicate axis in the arrangement of its pyrenoids, 

 which rarely occupy the centre of the chloroplast. G. achondroides 

 differs from G. dlplosporum in having pyrenoids in the lateral lobes of 

 its chloroplast as well as in its central axis. In G. pseudoconnatwn the 

 chloroplast is axile with four wedge-shaped masses radiating towards the 

 periphery, each mass possessing typically one pyrenoid. G. ornatiim 

 and G. Ralfsii differ from all the other species examined in having 

 scattered pyrenoids, rarely more than three in G. ornatumy but more 

 numerous in the larger G. Ralfsii ; and the chloroplast of the latter 

 resembles those of certain thick-celled species of Micrasterias. Many 

 species of Gosmarium have two axile chloroplasts in each semi-cell, there 

 being one point of pyrenoid formation in each chloroplast. The axis 

 which contains the pyrenoid or group of pyrenoids is surrounded by a 

 number of radiating plates or more numerous string-like projections, 

 whose peripheral edges in many cases spread out over the internal 

 surface of the cell-wall, either in irregular parietal masses or as a more 

 or less continuous reticulated film. Two forms of G. prsemorsum were 

 examined, containing one and two chloroplasts in a semi-cell respectively. 

 G. BreMssonii has most peculiar and variable chloroplasts, sometimes 

 parietal, sometimes distributed throughout the cell. A few species 

 have chloroplasts entirely parietal, with scattered pyrenoids, the number 

 of both beino^ variable. A. G. 



