ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 277 



US to stagnation or movement of the water. He maintains that study 

 <3arried out on those lines would help to solve problems of many kinds, 

 and to define the physiological relations which govern the species-limits 

 of Cryptogams. E. S. 6. 



New and Rare Fresh-water Algae. — CI. I. Playfaib, {Proc. Linn. 

 Soc. Netv South Wales, 1918, 43, 497-543, 5 pis. and 11 figs.). An 

 enumeration, including 28 species, 29 varieties, 9 forms, and 1 genus, 

 all new to science, and figured and described. One collecting spot, 

 frequently visited during two years, was a pool which received the 

 drainage of a swamp after rain, and often dried up at other times. Its 

 flora was remarkably varied ; though the Desmids and Diatoms re- 

 mained fairly constant, yet the Myxophycete, Yolvocacefe, and Proto- 

 coccoideas presented month after month an apparently endless succes- 

 sion of forms— new, rare, or not previously recorded, and often never 

 seen again ; for example, 10 forms of Chlamydomonas, 5 of Garter ia, 

 2 of Phacotus, 2 of Vol vox, 7 of Oocystis, 7 of Tetraedron, 4 of Geminella 

 — which rarely were recorded again for the pool, but sometimes appeared 

 at the same time in some other pool at a distance. The new genus 

 is Urnella, placed in the Hydrogastracese ; it contains one species, 

 U. ierrestris, found as a green growth on a clay path in very wet 

 weather. It somewhat resembles Protosiphon and Codiohim, but differs 

 from both. Every novelty appears to be figured. A. G. 



Fresh-water Algse of Africa. — F. E. Fkitsch (Annals S. African 

 Mus., 1919, 9, Pt. 7, 483-611, 43 figs, in text). A first report of the 

 Fresh-water Algse, mostly from the Cape Peninsula, in the herbarium of 

 the South African Museum. The collections here dealt with were made 

 in the year 1908 by a number of different botanists, and contain 

 97 genera and 238 species, of which 19 species and 6 varieties are new. 

 The list is not in any way regarded as exhaustive, since several common 

 genera are quite unrepresented, while of others only one or two species 

 have been found. Two new species of Echallocystis and one of Splisero- 

 plea are described. Hydrodictyon africanum is also recorded. Many 

 of the species are discussed in detail and figured. E. S. G. 



Green Algae of North America : Second Supplement. — P. S. 

 Collins {Tvfis College Studies, 1918, 4, No. 7, 106 pp., 3 pL). This 

 second supplement embodies all additions to the subject published or 

 discovered during the last five years. Keys to certain genera are 

 revised, a few new species are described, and valuable critical notes are 

 appended to many of the records. E. S. G. 



Working Key to the Genera of North American Algae. — F. S. 

 Collins {Tufts College Studies, 1018, 4, No. 8, 50 pp.). A practical 

 key, including all well-established North American genera, omitting 

 Diatomacese and such intermediate organisms as Peridiniacese, Flagellatse, 

 etc. A useful novelty is the employment of geographical distribution as 

 an aid to generic determination. In the cases where a genus is recorded 



