ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 489 



Germination of Ustilago Maydis.* — Dr. G. Beck has observed 

 the germination of the resting-spores of this fungus, and the penetra- 

 tion of the germinating tubes into the tissue of the host, the processes 

 being in every way similar to those of Tilletia. The spores are usually 

 produced singly at the ends of large sac-like branches, which are 

 formed either irregularly at different spots of the hyphae or in 

 regular rows. Sometimes they branch dichotomously, and then 

 develope two spores instead of one. 



Exoascus.f — According to Prof. E. Sadebeck the ascospores are 

 not formed in the ascus of Exoascus flavus and alnitorquus by free 

 cell-formation, but by cell-division. The ascogenous cells are at first 

 spherical and entirely filled with protoplasm in which is a distinct 

 nucleus. As the cell developes into an ascus, it elongates in a direc- 

 tion vertical to the surface of the organ of the host, and assumes a 

 cylindrical form. During this period the various stages of division 

 of the nucleus can be followed in the interior, displaying the appear- 

 ance of the nuclear figures, nuclear spindles, and equatorial plates, 

 &c., altogether corresponding to the same processes in the higher 

 plants. Only after the development of two nuclei by division of the 

 original nucleus, does a membrane appear between the two nuclei, 

 completing the differentiation of the organ into ascus and pedicel-cell. 

 The eight ascospores are formed in precisely the same way within the 

 ascus by three successive bipartitions from a single nucleus, following 

 very rapidly one after another. Dr. Fisch has found the processes 

 to be precisely the same in Ascomyces endogenus, a hitherto unde- 

 scribed species. 



The author enumerates twelve species of Exoascus, of which four 

 are here described for the first time. He classifies them under two 

 great groups. In the first the mycelium is persistent in the interior 

 of the tissue of the host, putting out only at the beginning of a new 

 period of growth in the host branches which reach the epidermis, 

 where a new system of hyphse is then formed between the epidermis 

 and the cuticle. The fertile hyphae are entirely used up in the 

 formation of the asci ; these are not closely crowded, and when the 

 ascospores are being developed, stand on a pedicel-cell separated from 

 the ascus by a septum. In the second group the mycelium persists 

 only beneath the cuticle, and spreads only between the epidermis and 

 cuticle at the commencement of a new period of growth in the host ; 

 the fertile hyphee being formed only in the leaves of the young shoots. 

 The fertile hyphae may or may not be entirely used up in the production 

 of the asci. 



The author describes the nature of the ravages on the host 

 committed by various species of Exoascus, especially E. alnitorquus 

 on the alder, and E. TJlmi on the elm, and the best modes of getting 

 rid of the disease, dependent on the different modes of life of the 

 different species as described above. 



* Verhandl. K. K. Zool.-Bot. Gesell. Wien, xxxv. (1886) pp. 28-9. 

 t Jahrb. Wiss. Anstalten Hamburg, L (1884). See Bot. Centralbl., xxv. 

 (1886) p. 168. 



Ser. 2.— Vol. VI. 2 K 



