ZOOLOGY AND BOTANY, MICROSCOPY. ETC. 195 



alternation of generations in Polysiphonia, with the period of chromo- 

 some reduction at the time of tetraspore formation. 



The author finds that the carpospore on germination shows 40 

 chromosomes, and the tetraspore 20, and, since in the vegetative mitoses 

 ■of the tetrasporic and sexual plant the same numbers appear respectively, 

 he infers that tetrasporic plants come from carpospores and sexual plants 

 •come from tetraspores. The nuclei of the gametes (sperm and carpo- 

 gonium) contain each 20 chromosomes. The fusion nucleus in the 

 fertilised carpogonium as a result has 40 chromosomes, and gives rise 

 to a series of nuclei in the central cell. Some of these enter the carpo- 

 spores, which are consequently a part of the sporophytic phase to be 

 ■continued in the tetrasporic plant. The gametophyte nuclei in the 

 central cell of the cystocarp with 20 chromosomes break down. 

 Tetraspore-formation terminates the sporophytic phase with typical 

 reduction phenomena, so that the tetraspores are prepared to develop the 

 gametophyte generation. The cystocarp is included as an early part of 

 the sporophytic phase. 



New Coralline Algae.* — M. Foslie and M. A. Howe describe two 

 new species of CoralHnes from the Island of Culebra, lying between 

 Porto Rico proper and St. Thomas. They are Goniolithon acropetum 

 and Lithophyllum aiitillarum. The former is, probably, most nearly 

 allied to G. frutescens Fosl. f . fiahelliformis of the South Pacific, but is 

 coarser, more anastomosed, often much more widely dilated, and more 

 conspicuously decutescent. It also differs in its conceptacles and 

 sporangia. L. aiitillarum is a reef -builder, and bears some resemblance 

 to coarse forms of L. africanum Fosl. and L. craspedium Fosl., another 

 South Pacific species. 



Normal and Abnormal Germination in Fucus.f — E, Kiister dis- 

 cusses the result of some experiments which he undertook with a view 

 to testing the statements of Rosenvinge concerning the germination of 

 fertilised oogonia of Fticus. That author maintained that the direction 

 of the first cross-wall and the development of polarity in the germinating 

 egg were influenced by external factors. Kiister examined Fucus serratus 

 and F. platycarpus, and his results confirm in general those of Rosen- 

 vinge. He finds that in a typical course of germination only one rhizoid- 

 papilla arises on the egg, but there are exceptions, and these he describes 

 and figures, showing also the manner in which he was able to bring this 

 about. He concludes by stating that the normal course of development 

 is hindered or prevented by osmotic disturbances : and he considers it 

 possible that certain osmotic conditions in the egg determine the place 

 of formation of the rhizoid — a theory which is in keeping with the 

 results of experiments on Facus, Pelvetia, and Cystoseira. 



Renfrewia, a New Genus.J — R. F. Griggs describes a new genus of 

 Laminariacege, distinguished from Laminaria by having a simple discoid 

 holdfast without haptera. The type species of the genus is R. parvula, 

 which, from its small size and evident simplicity of structure, may be 



* Bull. Torrey Bot. Club, xxxiii. (1906) pp. 577-80 (4 pis., figs, in text). 



+ Ber. Deutsch. Bot. GeselL, xxiv. (1906) pp. 522-8. 



X Postelsia, Year Book Minnesota Station, 1906, pp. 247-74 (figs, in text). 



o 2 



