ZOOLOGY AND BOTANY, MICROSCOPY. ETC. 793 



other bulbs besides those of Eucharis. The fungus which occurs in the two 

 forms o{ ^cidiitm depaupemns and P«ca'wza asf/ra, is exceedingly destructive 

 to cultivated sjiecies of Viola. 



Tubercles on Ruppia rostellata and Zannichellia polycarpa produced 

 by Tetramyxa parasitica.* — Dr. E. Hisinger has examined the structures 

 produced by this Myxomycete. The cycle of development was fully 

 followed out, including the formation of the tetraspores. The parasite 

 attacks in the first place the youngest and tenderest tissues of the host, and 

 the course of injury is very similar to that produced by Plasmodiophora 

 Brassicge. 



Protophyta. 



Oidium albicans. f — Dr. H. C. Plaut finds that this organism developes 

 by sprouting and by the formation of mycelia from gonidia. The resting 

 spores described by Grawitz and others he suspects to be merely conditions 

 of involution, while the sporangium of Baginski is undoubtedly an involu- 

 tion form. The author next discusses Monilia Candida Bon., growing on 

 rotten wood. This, transferred to the mucosa of the crop of fowls and 

 pigeons, was found to be indistinguishable from Oidium albicans. 



Cultivations made from such material always retained the biological and 

 physiological characteristics of the true Oidium cultures. The inference 

 drawTi is that 0. albicans and Monilia Candida Bon. are identical, and the 

 author proposes that the former should be known as Monilia Candida. 



This organism is easily destroyed by sublimate solution, and is not 

 transferable to the healthy mucous membrane of animals with a " strong 

 constitution." 



Heterocystous Nostocacese.:]: — The concluding part of MM. Bornet and 

 Flahault's exhaustive account of the heterocystous Nostocacefe contained in 

 the principal French herbaria is devoted to the tribes Sirosiphoniacete and 

 Scytonemacese. The former are characterized by the cells dividing in the 

 direction of the length of the trichome, and by branches resulting from the 

 development of one of the collateral cells formed by this division. The 

 sheath may be either closed or continuous ; only in Mastigocoleus do certain 

 branches terminate in hairs. The heterocysts occupy the place of an entire 

 cell -when the trichome is formed of cells not divided longitudinally ; other- 

 wise at the expense of one of the peripheral collateral cells. Seventeen 

 species are described in detail, belonging to five genera, growing in stagnant 

 water or on damp rocks, several in thermal springs, only one in salt water. 

 The genera Mastigocoleus, Hapalosiphon, Stigonema (including Sirosiplion^, 

 and Capsosira make up the subtribe Stigonemeee, distinguished by having a 

 definite outline ; the subtribe Nostochopsideas, in which the sheaths coalesce 

 externally into an amorphous gelatinous mass, comprises only the mono- 

 typic genus NostocJwpsis from America and Sumatra. 



In the Scytonemacefe the trichomes never terminate in hairs, and the 

 cells never divide longitudinally. The filaments are simple only in Micro- 

 chsete ; in the other genera branches emerge from the sheath either imme- 

 diately below a heterocyst, or from the middle of an interval between two ; 

 the sheath is continuous, and frequently coloured; the heterocysts are 

 intercalary or basilar, solitary or in rows. Seven genera are described, 



* Meddel. Soc. pro Fauna et Flora Fennica, 18S7, 8 pp. and 10 pis. See Kev. 

 Mycol., ix. (1887) p. 168. 



t Plaut, H. C., ' Neue Beitrage zur systematisclien Stellung des Soorpilzes in der 

 Botauik,' 32 pp., 12 figs., 8vo, Leipzig, 1887. 



X Ann. Sci. Nat.— Bot., v. (1887) pp. 51-129. Cf. tln:^ Journal, ante, p. 449. 



