Biologie. — Cytologie und Befruchtung. 103 



ration and a gametophytic plant. He holds that the generations 

 in Hydrozoa do not alternate in the botanical sense, and points 

 out that although reduction of the gamete bearing generation 

 has not been proved for animals, there is strong evidence for 

 its having occurred in plants. M. A. Chrysler. 



Ostenfeld, C. 11, PreliminaryRemarks on the Distri- 

 bution and the Biolog y of the Zostera of the Danish 

 Seas. (Botanisk Tidsskrift. XXVIII. K^benhavn 1905.) 



In the danish seas Zostera grows down to different depths in diffe- 

 rent piaces, the greatest depth being about 11 m. The maximum depth 

 depends on the transparency ot the sea water (in summer) which can 

 be determined by means of a white disk let down in the sea. 



On Sandy boiioms, Zostera is always rather small and narrow-leaved, 

 in muddy and sheltered piaces it reaches its richest development from 

 about 3 m. downwards to 10 m., and the author has found no distinct 

 difference in the development of specimens growing at 3—5 m. from 

 others growing at 8 — 10 m. Consequently the development depends on 

 the character ot the bottom (the soil), not on the deplh in which the 

 plants grow. 



The Zostera loses its long summer leaves in the autumn ; the leaf 

 breaks at the point where sheath and blade meet, and this shedding of 

 the blades causes the large masses of dniimg Zostera, which everybody 

 knows. 



The flowering season begins at the end of June and continues until 

 autumn, but the latest flowers do not ripen their fruils.f' In the first days 

 of August the first fruits are ripe. — The flowering shoots also break off 

 in autumn. — Seedlings are very rare, the vegetative propagation-modus 

 seems to be the most common one. Paulsen (Copenhagen). 



Chamberlain, Charles J., Methods in Plant Histology. 

 Second Edition. (Chicago: The University of Chicago 

 Press. 1905. X, 262 pp. figs. 88. Doli. 2,25.) 



Chamberlain has revised and iargely rewritten his Me- 

 thods in Plant Histology, adding several new chapters and 

 elaborating and in many instances shortening the processes The 

 added chapters deal with microchemical tests, free- band sections, 

 special methods, the use of the microscope, and a chapter dea- 

 ling with staining and mounting filamentous algae and fungi in 

 Venetian turpentine. In this chapter an abstract of the methods 

 of Pfeiffer and Wellheim is given, together with such mo- 

 difications as have been found to give more successful prepa- 

 rations. The Venetian turpentine method, which gives prepa- 

 rations as hard and durable as baisam mounts, should almost 

 entirely replace the glycerin method. 



Much attention is given to collecting and keeping material 

 alive in the laboratory. Klebs' methods of securing reproduc- 

 tivt phases in algae and fungi are presented in a practical 

 manner. Specific directions are given for making such prepa- 

 rations as are needed by teachers and by those who wish to 

 get a comprehensive view of the plant kingdom from the lowest 



11* 



