ZOOLOGY AND BOTANY. MICKOSCOPY, ETC. 841 



whicli do divide give birth to the mother-cells of the spores. In the 

 formation of the latter no cell- wall is formed between the daughter-cells, 

 which are separated only by mucilage ; and this process is repeated 

 many times ; this gelatinous substance surrounding the mother-cells 

 like a true membrane. Finally the spores surround themselves by a 

 thick membrane. The elatcrs are also at an early stage surrounded 

 by a thin gelatinous membrane like that of the sjjores ; their proto- 

 plasmic contents gradually diminish, and are at least partly con- 

 sumed in the formation of the spiral, the development of which 

 resembles that of spiral vessels as described by Strasburger. By the 

 time this spiral is completely developed, the protoplasm in the 

 interior of the elater has entirely disappeared. 



Trochobryum, a new genus of Mosses.* — Herren J. Breidler and 

 G. Beck give the following diagnosis of this new genus of Seligeri- 

 acesB : — Dwarf plants, with the nearest affinity to the genus Seligeria. 

 Leaves loosely areolated from a short base, subulate, with a long 

 projecting mid-rib. Capsule seated on a thick seta, sub-spherical, 

 thick-walled, with a short indistinct neck, depressed when dry ; sub- 

 disciform or of a shallow funnel-shape when the operculum is 

 removed. Peristome-teeth 16, equidistant, hygroscopic, rather broad, 

 without any dividing line. Operculum adnate to the columella, 

 apiculate. Calyptra hooded. The only species, T. carnioUcum, is from 

 calcareous rocks in Carniola. 



Algae. 



Physiological Anatomy of Algae.f — Herr N. Wille has made 

 observations on the elasticity of the tissue of the larger marine algte, 

 by means of which they are able to resist the traction and other 

 distorting forces of large waves. The faculty of stretching he found 

 to be very considerable in the larger Floridete, and still greater in the 

 Laminarieae, varying from 25 per cent, in Porpliyra vulgaris to 48 per 

 cent, in Laminaria flexicaulis. The " leaves " of seaweeds are almost 

 invariably flexible ; while on the other hand, the " stem " may have 

 considerable firmness ; and this firmness may be imparted in three 

 diflferent ways, viz. : — (1) by the whole of the interior being occupied 

 by strongly thickened cells, as in AhnfeUia pUcata ; (2) by incrusta- 

 tion, as in Corallina officinalis ; (3) by columnar haptera, as in the 

 Laminaricse, where the walls of the outer cells are more strongly 

 thickened than those of the central cells. 



Contrivances to prevent traction are very common. The cell-walls 

 towards the base of the stem are thicker in Chorda Jilum, while this 

 organ itself is stouter in Polysiphonia, Ehiziues are formed for the 

 same purpose outside the membrane of tlie mother-plant, consisting 

 of single rows of cells in Cladophora ojjhiophila, of plates of cells in 

 M(/no8troma orhiculatum ; or within the mother-plant, of rows of colls 

 in Cladophora rupestris and Bangia, of plates of cells in Porphyra 



* Vorh. K. K. Zool.-Bot. GohcU. Wien, xxxiv. (1885) pp. 105-G (1 pi.), 

 t HIi. li^.t. Hallbk. Btockholm, Nov. I'J, 1884. Hte I3ot. Ccutralbl, xxi. (1885) 

 pp. 282 anil 315. 



