ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 279 



American Desmids.* — M. G-. Lagerlieiin states the number of species 

 of DesmidieBB at present known in the New World at about 600 ; the 

 American flora is distinguished by the large number of species of Pleuro- 

 tseniiim and Arthrodesmus, and by one genus, PJiymatoclocis, not yet found 

 in Europe. Many of the American desmids belonging to the genera 

 Cosmarium, Arthrodesmus, and Xantkidium, have remarkable thickened 

 membranes, more or less yellow, and pitted along the median furrow. 



Pyritized Diatoms.f — Dr. A. A. Julien states, with regard to " pyritized 

 diatoms," that the material referred to by all writers under the broad name 

 of pyrites, consists substantially of the single mineral pyrite. To deter- 

 mine this point, he searched for minute cavities in which the substance 

 might have found opportunity to crystallize, and discovered not only minute 

 drusy surfaces, but also little spherules covered by projecting crystals. 

 The globules which Mr. Kitton detected appear to have been round and 

 smooth, probably concretionary. On those which he discovered may be 

 seen triangular faces, which appear to belong to octohedra ; these crystals 

 must therefore consist of pyrite. This conclusion is confirmed by a 

 specimen of fossil fruit converted into pyrites from the London clay at 

 the Isle of Sheppey. This drusy surface shows distinct sharp octohedra 

 of larger size, so that this crystalline form probably prevails in the pyrite 

 crystals throughout the London clay. The true colour of the pyrite films, 

 ■when examined on a fresh cross fracture, appears to be a greyish-white. 

 This indicates that the crystals are far from pure, probably mixed with a 

 large proportion of marcasite. The incipient decomposition of the mineral 

 is characteristic of the presence of marcasite, beginning with a golden- 

 yellow tarnish within, and assuming a bronze colour without. As the 

 decay progresses, the valves become covered by a reddish film of iron oxide, 

 and finally the entire material passes into reddish-brown iron-ochre, some- 

 times blackened as if by the intermixture of oxide of manganese. The 

 mode of deep subterranean decomposition is, therefore, hepatic, and vitrio- 

 lescence is never observed in these altered diatoms ; although the latter 

 form of decay attacks the nodules of pyrites lying nearer the surface in the 

 London clay, at other points along the Thames, as at the Isle of Sheppey. 



Iiiclienes. 



Receptacles for reserve-materials in Lichens, j — Herr H. Zukal finds 

 in the hyphal system of some lichens, especially on the under side, rows or 

 clusters of swollen spheroidal cells which may attain a diameter of 15 /i. 

 They are most abundant in species of Verrucaria, but are by no means 

 invariably present in them, and occur also in other genera. By the applica- 

 tion of micro-chemical tests, they were found to contain a fatty oil, and the 

 author suggests that they serve as reservoirs of food-material for the 

 formation of fructification. 



Ftingi. 



Endogenous Production of Spores.§ — Pursuing his investigations on 

 the mode of production of the spores of fungi, M. J. de Seynes states that 

 a considerable number which are usually described as exogenous are in 



* Oefver. K. Vetensk. Akad. Forh. Stockholm, 1885, pp. 225-55. See Bull. Soc. 

 Bot. France, viii. (1886), Rev. Bibl., p. 159. 



t Journ. New York Micr. Soc, ii. (1886) pp. 85-96. 



X Bot. Ztg., xliv. (1886) pp. 761-70 (2 figs.). 



§ De Seynes, J., ' De la production des corps reprodncteurs appele's acrospores,' 

 51 pp. and 3 pis., Paris, 1886. See Bull. Soc. Bot. France, viii. (1886), Eev. Bibl., 

 p. 145. Cf. this Journal, 1886, p. 832. 



