76 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
these protoplasts being metamorphosed over into autospores. The 
pyrenoid disappears after the first cleavage, new pyrenoids being formed 
de novo in the young autospoi^s. A. Gepp. 
Addition to our Knowledge of Oscillatoriaceae. — A. C. J. van Goor 
(. Rec . trav . hot. Neerland ., 1918, 15 , 255-9, 1 pi. ; see also Nuova 
Notarisia , 1921, 32 , 168). Descriptions are given of four new species 
of Oscillatoria and one of Lyngbya , collected in lakes and ditches, etc., 
in various parts of Holland. E. S. G-. 
On the Fossil Algae of the Petroleum-yielding Shales of the 
Green River Formation of Colorado and Utah. — C. A. Davis ( Proc . 
Nat. Acad. Sci. Washington D.G. , 1916, 2 , 114-19 ; see also Bot. 
Centralbl., 1919, 140, 164). The region in question consists of large 
areas of, generally, carbonaceous shales, exceeding in places 8000 ft. in 
thickness, and yielding petroleum. The ground mass seems to have been 
originally vegetable matter, and contains a large percentage of low algae. 
Three distinct types have been discovered (1) A very considerable 
number of cellular, filamentous, and gelatinous forms clearly belonging 
to Oyanophyceae. One of these can almost certainly be referred to 
jSpirulina. (2) Somewhat less common forms belong more or less 
certainly to Chlorophyceae. One resembles Pediastrum in all essentials ; 
another type has been noted with spiral chloroplasts, like Spirogyra. 
(3) Unclassified algae, which cannot at present be placed with any 
known living species. E. S. G. 
Cell-membrane and Cell-division of Ciosterium Nitzsch. Critical 
Remarks.— J. Lutkemuller ( Ber. Deutsch. Bot. Gesell., 1917, 35, 
311-18 ; see also Bot. Centralbl., 1919, 140, 138). A challenge to 
statements of van Wisselingh. That author denied segmentation of the 
cell-wall of Ciosterium ; and maintained that the older part of a cell 
which had undergone division must possess more layers of cell-wall than 
the younger part, since a new layer must be added at each division. An 
examination of C. turgidum Ehrb. subsp. giganteum Nordst. shows 
segmentation ; and the number of layers in the cell- wall was always the 
same in both halves. On the other hand, it is true that several of the 
layers are the richer in cellulose the nearer they lie towards the centre 
of the cell. The author shows by means of figures that in species of 
Ciosterium with growth subsequent to cell-division the number of sutures 
is even where there is one median girdle, and uneven where there are 
two ; which proves the correctness of the statement that typical 
periodical subsequent-growth takes place in girdled Ciosterium species. 
Irregular girdle formation was found in about 3*5 per 1000 cases, a 
proportion which is negligible. It occurs in C . didymotocum Corda, 
C. Baileyanum Breb., and C. costatum Corda, which are otherwise 
vegetatively normal, and in which zygospores are unknown. If many 
such cases occurred in Ciosterium, van Wisselingh would be correct in 
regarding the presence or absence of girdle formation as having no 
systematic value. E. S. G. 
Characteristics of some Coscinodiscineae. — A. C. J. van Goor 
{Rec. travaux bot. Neerland., 1920, 17 , 1-25, figs. ; see also Nuova 
