522 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Fertilisation and Spore-Ripening in Mosses.* — A. Grirnrne has 

 carefully studied the time when fertilisation occurs in a large number of 

 mosses growing in Thuringia and Lower Hesse, and the subsequent 

 period that elapses until the spores are ripe. All previous records, save 

 those of Arnell for Scandinavian species, he finds to be untrustworthy. 

 The maturity of the antheridia and archegonia is attended by certain 

 characteristic appearances which are pointed out. The archegonia 

 persist for a much shorter period than the antheridia ; hence a monoicous 

 inflorescence may appear to be unisexual. Self-fertilisation may be 

 prevented by dichogamy ; but the author does not believe that cross- 

 fertilisation is of any real advantage to mosses. Sterility is mainly due 

 to the coincidence of dry weather and a dioicous inflorescence. The 

 distribution of antherozoids is brought about by the movements of 

 creeping insects, &c, or by the splash of rain-drops. As to spore- 

 ripeness, the ordinary records are useless and misleading ; it varies with 

 the climate. The characters that betoken spore-maturity are pointed 

 out. The detaching of the operculum in herbarium specimens is no 

 satisfactory guide as to the natural time of ripeness. The author sup- 

 plies a table indicating in parallel columns the exact seasons of fertili- 

 sation and of spore-ripening, and' the duration of sporogonial develop- 

 ment, of 207 Thuringian species ; and for comparison he adds the 

 corresponding results obtained by Arnell in Scandinavia, as well as the 

 times of spore-ripeness recorded by Limpricht. The period of inflores- 

 cence is short and definite for each given species, usually one to two 

 weeks. 177 of the species were examined by both the author and 

 Arnell : in 109 of these it is found that the period of sporogonial 

 development is longer in Germany than in Scandinavia. The longest 

 time observed in Germany is 24 months (Grimmia ovata), and the 

 shortest is 4 months (Catharinea teneUa). In the majority of German 

 mosses it approaches two years. Self -fertilisation is the rule in herma- 

 phrodite species ; the antheridia and archegonia are mature at the same 

 time and thus tend to make cross-fertilisation impossible. 



Riella.f — M. A. Howe and L. M. Underwood give a short account 

 of the morphology of the curious aquatic genus Riella, which was 

 supposed to be confined to the Mediterranean region until last year when 

 a species from Turkestan was described. Two more new species are 

 described, from Texas and the Canary Islands, raising the total to nine 

 species. GemmaB were found on the American specimens, and were 

 cultivated to enable their development to be described. An account is 

 also given of the spore-germination of both species. 



SphsBrocarpus terrestris.J — I. Douin, having noticed several erro- 

 neous statements about Splicer ocarpus terrestris in various descriptive 

 floras, has drawn up a careful and detailed account of the structure and 

 development of the plant, illustrated with a number of figures. He 

 compares it with Riccia sorocarpa and other hepatics. He has never 

 found it to be otherwise than dioicous. He describes the nervation, 

 branching, and growth of the thallus, the position of the involucres, 



* Hedwigia, xlii. (1903) pp. 1-75 (1 pi.). 



t Bull. Torrey Bot. Club, xxx. (1903) pp. 216-24 (2 pis.). 



% Rev. Bryol., xxx. (1903) pp. 44-57 (fig?, in text). 



