ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 40^ 



is followed by a separate discussion on each of the three ponds, with 

 the constituents and periodicity of their respective floras. Eucli contains 

 a small number of genera and species not observed in the others. Many 

 of the diatoms exist all the year round, a small numl)er showing a 

 maximum development either in cold or in warm water. The other 

 algte show in general a maximum from August to October. Intermediate 

 forms between several species and varieties of diatoms were observed. 

 Among the seventy-eight samples taken, one form occurs sixteen times. 

 It is here figured as a new variety minor, of Navkula cuspidata Kiitz. 



E. 8. (J. 



Study of the Cell-structure of Small Algae, with Special Reference 

 to Porphyridium cruentum Naeg. — F. Brand {Ber. Dmtsch. Bot. Ges., 

 1917, 35, 4:54-9 ; see also Bot. Gentralhl, 1919, 140, 107). Although 

 single species of algae cannot as a rule be determined by cell-structure 

 alone, still it is possible to limit certain groups by means of this 

 character, aud then to determine its members by a study of the 

 physiological, biological and functional conditions. Certain important 

 points in a study of cell structure are indicated. Too much value must 

 not be placed on culture and chemical treatment, on account of th" 

 great variability of these algfe. In cultivated material pathological 

 deformities frequently arise. The only material suitable for delicate- 

 cytological investigation is that in Avhich the majority of the cells, on a 

 preliminary examination under a medium-power objective, appear fresh, 

 absorb a stain in a living healthy manner, and show their homogeneity 

 by the presence of all intermediate forms. These conditions are only 

 to be obtained as soon as possible after collection. The author then 

 proceeds to demonstrate the evil results of an exclusive use of cultivated 

 material, as exemplified by Staehelin's work on Porphyridium cruentum, 

 supposed by him to possess a Cyanophyceous nature. The severe 

 criticism of this work of Staehelin is due to a wish to prevent the 

 incorporation of serious errors in literature. The chromatophore of 

 Porphyridium differs from the external coloured protoplasm-layer of 

 Cyauophyce^e, which is almost unchangeable in form and position, not 

 only in its Floridean red colour, but also in the variability of its form. 

 Further, it can be displaced by the occasional appearance of sap-vacuoles. 

 Also there is no mistaking the pyrenoid of a normally vegetating living 

 cell of Porphyridium. Staehelin's view on the appearance of peripheral 

 grains is also corrected. E. S. Gr. 



Results of a Study of the Myxophyceae. — A. Borzi (^Nuov. Giorn. 

 Bot. ltd., 19U. 21, 307-60 ; 191G, 23, 559-88 ; 1917, 24, 17-80, 

 65-112, 198-208, 209-14, 5 pis.). This paper embodies the mature 

 views of the author founded on observations made during the last 

 twenty-five years, during which time he has accumulated material for 

 adding to his notes published in the same journal, 1879-1882. The 

 work is divided into two parts. Part I. contains an Introduction in 

 which the gradual advance of the knowledge of Myxophyceae is described 

 up to the present day, aud an indication is given of the problems yet 

 to be solved. This is followed by a discussion on the general characters 

 of the group under the following headings :— Schizophyta and Myxo- 



2 F 



