442 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Hungary and Norway. The genus is characterized by each cell of the 

 cylindrical unbranched filaments containing two nuclei of unequal size ; 

 the dissepiments of the cells are also of unequal thickness. There is in 

 each cell one parietal chlorophore. Multiplication takes place by bipar- 

 tition of intercalary cells, no zoospores having at present been detected. 

 Each vegetative cell appears to consist of two parts, one older with a larger 

 nucleus and a thicker dissepiment, the other younger with a smaller nucleus 

 and a thinner dissepiment. In one stage resting-cells appear to be formed 

 in the same way as in some other Confervoideag. 



Layer of Earth composed of Algae.* — Prof. V. B. Wittrock finds near 

 Stockholm a layer of soil 0*2-0 '6 metres in thickness, at a little depth 

 below the surface, composed chiefly of filaments of Vaucheria, with which 

 some diatoms and remains of flowering plants were intermixed. The 

 species could not be determined. 



Intermediate Bands and Septa of Diatoms.f — By the term "inter- 

 mediate bands" (Zwischenbiinder) Herr O. Miiller designates certain 

 bands which are found in many diatoms between the valves and the girdle- 

 bands, formed after the development of the young valve, but before the 

 appearance of the young girdle-band. They must be regarded, like these 

 structui'es, as independent members of the cell-wall. There may be one 

 only or several of these bands in each half of the cell ; in the latter case 

 the number in the two halves is often unequal. The sjiace inclosed by the 

 valves and the intermediate bands is often divided by septa, which is never 

 the case with the space iuclosed by the girdle-bands. The intermediate 

 bands are either continuous annular portions of the membrane, like the 

 girdle-bands, or are open bands. Grammatophora maxima is described as 

 aftbrding a typical example of a species with a single intermediate band ; 

 in TabeUaria each half-cell has several ; and in Odontidium hyemale at least 

 two; while the genus JRhizosolenia furnishes species with a large number 

 of open bands which are not septated. 



Movement of Diatoms. :}: — In the valves of certain diatoms. Dr. 0. E. 

 Imhof describes pores through which the protoplasm is protruded in fine 

 processes. The forms investigated were a large Surirella species and a 

 Campylodiscus found in the alpine lakes of the upper Engadiue. When the 

 sides of the Surirella were disposed at right angles to the glass a row of very 

 minute elliptical apertures could be detected along the edge of the empty 

 valves. The protrusion of protoj)lasm was also observed. The four sides 

 exhibit a large number of fine conical canals, occurring in a definite relation 

 to the familiar markings. These canals open on the edge of the sides as 

 noted above. Along the edge there runs a shallow gutter. Through each 

 tubule a fine process of protoplasm is protruded, and all are connected by 

 the strand lying along the gutter. Some permanent preparations were made. 

 The structure of Campylodiscus is essentially the same. Fuller details 

 are promised. 



Diatoms of the 'Challenger' Expedition. § — The Eeport on the Dia- 

 tomaccfe of the ' Challenger ' Expedition, by Count F. Castracane, com- 

 mences with a succinct but admirable account of the general structure and 

 biology of the group. The phenomena of conjugation and of the formation 



* Bot. Siillsk. Stockholm, April 27, 18S6. See Bot. Centralbl., xxix. (1887) p. 222. 

 t Ber. Deutsch. Bot. GesoU., iv. (1886) pp. 306-16 (1 pi.). 

 J Biol. Centralbl., vi. (1887) pp. 719-20. 



§ Keport of the Voyage of H.M.S. ' Challenger.' Botany, vol. ii., 178 pp. and 

 30 pis., 4to, London, 188G. 



