22 Aleae 



>=>"■ 



together with the number of occurrences noted between January 

 1912 and March 1914. The author finds that there is a well-marked 

 periodicity in the occurrence of the majority of the algae in these 

 ponds. The season of greatest diversity and abundance was from 

 February to April or May in the years recorded. This corresponds 

 to a period of variable rainfall, gradually ascending temperatures, 

 increasing light intensity, and of comparatively slight development 

 of animal life. As the temperature rises from May to July the algae 

 become greatly diminished, and many forms altogether disappear 

 until late in the foUowing October or early November. In 1912 there 

 was a secondary maximum in October and November, falling off again 

 in December and January; but in 1913 there was a slight increase 

 in December, and an apparently stationary condition in Januar}' 

 prior to the early vernal maximum (January to March) which fol- 

 lowed. The Protococcales and Ulotrichales are dominant somewhat 

 prior to the Conjugatae and Heterokontae, the Conjugatae dominating 

 every other form in April and Ma}-. One species of Spirogyra is 

 described, which is apparently a summer form. Ethel S. Gepp. 



Griffiths, B. M., On Glaucocystis Nostochinearmn Stzigs. (Ann. 

 Bot. XXIX. CXV. p. 423—432. 1 pl. July 1915.) 



The author describes this alga as unicellular, solitary, occurring 

 in Sphagnum bogs; ellipsoidal, 30—45 \i long by 18—25 /« wide, 

 with a small polar internal thickening at each end, and an external 

 equatorial thickening; cell- wall mainly of cellulose; chromoplast ot 

 strongly recurved and radiating blue-green bands, which break up 

 during cell-division; 2 or 4 or 8 daughter-cells are produced within 

 the mother-cell; nucleus 'open' during the resting stage, it is a sphe- 

 rical mass of delicate reticulate unstainable protoplasm, distinguished 

 from the general cytoplasm b}'^ containing no metachromatin 

 granules; it lies close against the cell- wall. During the division 

 stage, the nucleus contracts, becomes coarsely reticulate, moves to 

 the centre of the cell, and becomes stainable; it contains chromatin, 

 and has a nuclear membrane. The metachromatin granules of the 

 cytoplasm disappear; and the nuclear chromatin aggregates into a 

 large karyosome. This divides by transverse fission; so too does the 

 cytoplasm; the halves round off, and daughter-cell walls are formed. 



Glaucocystis probably belongs to the Cyanophyceae. because of 

 the 'open' nucleus, the" tendency of cytoplasmic division to take 

 place independently of nuclear division, and the presence of phyco- 

 cyanin in the chromoplast. On the other hand, the very high difife- 

 rentiation of the nucleus in the dividing stage, the elaborate 

 chromoplast to which the phycocyanin is confined, the formation ot 

 daughter-cells like those of" Oocystis, and the cellulose wall, are 

 features that separate the plant from all other Cyanophyceae, and 

 probably justifv its being placed in a special group of Cyanophyceae. 



Ethel S. Gepp. 



Grove, W. B., Pleodorina iUinoiensis Kofoid in Britain. (The 

 New Phytologist. XIV. p. 169—182. 11 figs. London 1915.) 



In March 1915 the author collected Pleodorina iUinoiensis in 

 cart-ruts at Harborne near Birmingham. He describes in detail 

 and figures the structure, movements and life-history of this alga. 

 He compares the genus with Eiidorina and Pandorina, and finds 



