228 SUMMARY OF CURRENT RESEARCHES RELATING TO 



void plants which, passing over the sexual stage, produced Aglaozonia 

 lobes. Temperature appears to exercise a great influence over the deve- 

 lopment of the generations. 



Structure of Padina Pavonia.* — Herr G. Bitter has carried out a 

 series of experiments for the purpose of determining the effect of a 

 reversal of position on dorsiventral seaweeds. When the light reaches 

 it on the dorsal side only, the spirally rolled up margin first becomes 

 flattened out, and then rolls up on the reverse side. Fructification 

 appears on the upper side of fronds treated in this way, but not in such 

 abundance as on the under side. Erect shoots are formed on both sides 

 of the tballus in alternate zones ; those on the upper are less developed 

 than those on the under side. 



New Mode of Formation of Colonies in Diatoms.f — Under the 

 name Cyclotella socialis sp. n., Heir F. Schlitt describes a diatom, 

 found by him in the Lake of Constance, characterised by a novel mode 

 of formation of colonies. From each cell-membrane there project to- 

 wards the interior of the colony a large number of very fine parallel or 

 somewhat divergent straight stiff needles or threads, which become inter- 

 woven with one another, and thus connect a number of individuals into 

 a colony. The author argues against the multiplication of the genera of 

 diatoms, especially on biological grounds. 



Diatoms of Kiel Harbour.J — In an exhaustive account of the section 

 Pennatas of the diatoms of Kiel Harbour, Herr G. Karsten enumerates 

 28 genera and over 200 species, about 20 of the latter being new. The 

 earlier portion of the work comprises a general treatise on the structure 

 and definition of the protoplasm-body of diatoms, the position of the 

 nucleus, the number, form, and position of the chromatophores, the 

 presence of pyrenoids, and the history of development of each species. 

 He insists on the inadequacy of characters drawn from the valves alone 

 for the determination of genera and species. Within each genus the 

 number and position of the chromatophores may be used as the first 

 character for classification. With regard to the movements of diatoms, 

 the author follows O. Muller in regarding the raphe as a highly de- 

 veloped motile organ. He maintains his previous classification of the 

 mode of formation of auxospores under four types, § giving further illus- 

 trations. The special home of the motile forms of diatoms is the shifting 

 sea-bottom. 



E,hopalodia.|| — From a study of a collection of diatoms from the 

 soda-region of El Kab, in Upper Egypt, Herr O. Muller gives a fuller 

 description of this genus, to which he refers several species hitherto 

 placed under Epithemia. An important diagnostic character of the 

 genus is that a canal-raphe runs along the ridge of the roof-shaped valve 

 in the direction of the central node. The mode of division is described, 

 and a monograph given of the section Epithemioideas. 



* Ber. Deutsch. Bot. Gesell., xvii. (1S99) pp. 255-74 (1 pi.). 

 t Tom. cit, pp. 215-21. 



X Wisseuscli. Mittheil. ; Com. z. Unters. d. deutschen Meere in Kiel, iv. (1899) 

 pp. 19-295 (219 figs.). See Bot. Centralbl., lxxx. (1899) p. 126. 



* Of. this Journal, 1898, p. 514. 



|| Hedwigia, xxxviii. (1899) pp. 274-88 (3 pis.). 



