740 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Haute-Sadne and of the Pyrenees, he passed on to a wide study (mostly 

 in conjunction with J. Oardot) of the mosses of North America and 

 tropical Africa, specializing more particularly in the moss-flora of 

 Madagascar, his knowledge of which was unapproached. His principal 

 works are the Prodrome de la Flore bryologique de Madagascar (1897), 

 his Essai sur les Leucoloma (1909), the 163 plates of Madagascar mosses 

 in Grandidier's Histoire physique, naturelle et politique de Madagascar 

 (1898-1905). In conjunction with Cardot, he described seven genera 

 and more than four hundred species. A list of his publications is 

 included. 



Thallophyta. 



Algae. 

 (By Mrs. E. S. Gepp.) 



Sexual Reproduction in Algae.* — B. M. Davis discusses the nuclear 

 phenomena of sexual reproduction in algee, outlining the advances that 

 have been made in cytological research on this subject, and including in 

 his remarks a consideration of the sporophytic generation. As regards 

 the problems of the origin of the sporophyte and the relations of the 

 sexual and asexual generations to one another (whether or not they are 

 essentially homologous or antithetic in the alternation of generations), 

 the author does not deal directly with them. But his sympathies are 

 strongly with the hypothesis of antithetic alternation of generations. 



Sheath and Mucilage of Fresh-water Algse.t — J. Yirieux writes 

 on his experiments with regard to the mucilage of fresh-water algge, and 

 gives the following conclusions. In the great majority of cases the 

 mucilages are of a pectic composition, and are coloured more or less 

 deeply by ruthenium, as well as by other characteristic reagents (old 

 aluin-haamatoxylin, etc.). This holds good for Chlorophyceee in general, 

 Desmidiese, Zygnemaceai, Diatoms, BatracJwspermum, Ghroococcus turyi- 

 dus, and certain species of Phormidium. The author, however, has 

 found in two species a sort of mucilage, which stains strongly with 

 anilin-blue, and is rapidly dissolved by a solution of potassium, applied 

 cold. These characters point to the presence of callose. Such callosic 

 mucilage, rare among plants in general, has hitherto been unknown 

 among algas. 



As regards the Cyanophyceee, the author has verified the statements 

 of Lemaire regarding the presence of schizophycose in the sheath. It 

 may be associated with several substances, cellulose (in Tolypotliryx 

 penirillata, and certain Scytonema), and pectin (in Nostoc, Glnsocapsa, 

 Scytonema, Tolypothrix). Sometimes there is added a brown colouring 

 matter (scytonemin, glceocapsin), which occurs frequently in aerial forms. 

 Again, certain sheaths, such as those of some Schizotlirix, are composed 

 of true cellulose. The author considers that of all the functions 

 attributed to the sheath or to mucilage only that of serving as a water 

 reserve is general. All the other functions are either very problematical 

 or they apply to a very limited number of types. Protection against 



* Amer. Nat., xliv (1910) pp. 513-32. 

 t Coinptes Reudus, cli. (1910) pp. 334-5. 



