ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 1 ( J7 



from the gametangia, and isogamous conjugation occurs. 4. The result- 

 ing zygospore divides and gives rise to a chain or mass of cells. These 

 may be of the " 2 x " type, or the reduction may occur in the early 

 divisions of the zygospore. 5. The cells of this structure rupture, and 

 their contents grow out and form the gametophyte. 6. The young 

 gametophyte consists of a flat lamina, one cell thick, and is attached at 

 its base to surrounding objects by a number of unicellular rhizoids. 

 7. The cells of the lamina divide, and eventually form the limiting and 

 cortical layers and part of the medullary tissue. 8. The stipe is formed 

 by a modification of the base of the lamina. 9. Part of the medullary 

 tissue is formed by an upgrowth of cells from the base of the rudimentary 

 stipe. 10. A disk-shaped expansion is formed at the base of the stipe, 

 and from this the hapteres originate. 



Dictyota dichotoma.* — W. D. Hoyt describes some interesting ex- 

 periments made by him on Dictyota dichotoma at the laboratory at Beau- 

 fort, North Carolina. The cultures were started in the laboratory and 

 then transferred to the harbour. The whole process is described, with 

 the methods employed for preventing contamination. The results of the 

 experiments show that the belief in alternation of tetrasporic and sexual 

 generations in I), dichotoma, previously based on cytological evidence 

 alone, is proved. The author summarises his conclusions as follows :— 

 Plants of D. dichotoma raised from fertilised eggs gave thirty-three tetra- 

 sporic plants and no sexual ones. Plants raised from tetraspores gave 

 sixty-four sexual plants and no tetrasporic ones. The tetraspores of a 

 single plant produced both male and female plants, in one case in about 

 equal numbers. 



Laboratory Cultures under Gas.f — Z. Woycicki was incited, by a 

 perusal of Pascher's work on Mougeotia, to undertake and publish some 

 investigations on certain filamentous Chlorophycese concerning their 

 growth, regeneration, and propagation in laboratory cultures and under 

 the influence of coal gas (Leuchtgas). He describes his results in some 

 detail, and at the end of his paper gives a clear summary. In certain 

 species of Spirogyra the influence of the gas is shown by disturbances of 

 the morphogenetic process, which lead to peculiar pseudorhizoidal hyper- 

 trophies. Hand in hand with this occur also changes in the contents 

 of the energids, as is seen in the degeneration of the chloroplasts and the 

 precipitation of tannin-albumen compounds in a finely granular mass. 

 Such a degeneration of the single energids of the filament produces a dis- 

 solution of these bodies in the gormogonial portions or in single cells, and 

 these make an effort to bring about regeneration of the individuals. This 

 regeneration does not, however, follow a normal course in certain species 

 of Spirogyra, but is associated with hypertrophies, which generally appear 

 in the end-cells of the new individuals. The degeneration and the 

 dismembering of the hypertrophied cells form distinct evidence against 

 the rhizoidal character of their outgrowths. Cladopltora fracta var. 

 horrida is far less sensitive in general than Spirogyra in laboratory cul- 

 tures. Under certain doses of coal-gas, however, it forms either aplano- 



* Bot. Gaz., xlix. (1910) pp. 55-7. 



f Bull. Internat. Acad. Sci. Cracovie, No. 8 (1909) pp. 588-6G7 (figs, in text). 



