82 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Marine Diatoms of France. * — The second part of this very fine 

 work, by H. and M. Peragallo, is devoted to the Pseudoraphideae, a 

 commencement being made also of the Anaraphideae, distinguished by 

 the central structure of the valves. The genera are arranged under 

 two tribes, the Biddulphioidse and the Discoidese. 



Schmidt's Atlas der Diatomaceen-Kunde.— Heft 57 of this work con- 

 tains the usual 4 plates of the customary excellence, viz. pis. 225-228. 

 It is chiefly devoted to the genus Stej)hanodiscus, but species of Cyclotella, 

 Coscinodiscus, and Tlialassiosira are also illustrated. 



Pseudenclonium, a New Genus of Algae.f— In the first seven instal- 

 ments of his studies on Chlorophycese, made at the biological station at 

 Drobak, Prof. N. Wille has a number of notes on the structure and life- 

 history of algre belonging to the Chlorophyceae, with descriptions of 

 several new species and forms, and of one new genus Pseudenclonium, a 

 marine genus of Chsetophoraceae. The thallus consists of an irregular 

 foot with irregularly branched cells, some of which form unicellular or 

 less often multicellular branched rhizoids. The terminal bristle is 

 wanting in the erect branches ; they branch irregularly, and often form 

 Pleurococcus-liko colonies. The cells have a parietal chlorophyll-disc 

 with a pyrenoid and a nearly central nucleus. Propagation takes place 

 by zoospores and akinetes. The zoospores are broadly ovate with four 

 cilia, but with no red eye-spot. The resting akinetes have a thick 

 membrane and yellow-green contents, and are surrounded by a gelatinous 

 envelope. 



Cladophora.* — Pursuing his researches on the structure of this genus 

 of Algae, F. Brand states that in young cells of aquatic species, in addi- 

 tion to the inner and outer layers of the cell-wall, there is always a 

 distinct outermost stratum, which can be detached by the application of 

 acetic acid. The membrane of old cells becomes thin at the spots where 

 adventitious branches are about to be formed, apparently by the action 

 of some solvent proceeding from the apical protoplasm, in the same way 

 that the cell-wall is completely absorbed at the spots where the zoospores 

 escape. A similar process, proceeding from the apical protoplasm, 

 appears to be the efficient cause of the layers which compose the hinge- 

 portion of the filament. The necessary pushing upwards of the base of 

 a branch in the process of formation is assisted by a corresponding in- 

 crease in the upper portion of the mother-cell. The most common form 

 of the chlorophores is reticulate ; there are all intermediate forms between 

 an elongated reticulum and isolated plates ; but the extreme cases do 

 not occur in ordinary vegetative cells ; the statement that spiral bands 

 have been observed in Cladophora is probably erroneous. The number 

 of nuclei in a cell is usually great, but they are often reduced to two, 

 and occasionally to one. 



* Les Diatomecs marines de France, '2 m0 partie, Paris, 128 pp. and 39 pis. Cf. 

 this Journal, 1890, p. 91. 



t Vidensk. Skrift. I. Math.-naturw. CI., 1900, No. V,, Christiania, pp. 1-46. See 

 Hedwigia, xl. (1901) Beibl., p. 73. 



X Beih. z. Bot. Central!)]., x. (1901) pp. 1S1-521 (10 figs.). Cf. this Journal. 

 1900, p. 92. 



