ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 501 



central body or nucleus, which in the stages between divisions is. except 

 for the absence of a limiting membrane, much like the resting-nuclei of 

 the higher plants. The nucleus contains a mesh of fine fibres, along 

 which small granules are scattered. The mesh is embedded in a clear 

 substance resembling nuclear sap. The mesh stains like linin, and the 

 granules like chromatin with Haidenhain's hamiatoxylin or Flemming's 

 triple ; although wanting a membrane, the nucleus is quite distinct from 

 the surrounding cytoplasm. As a cell of the Lyngbya approaches di- 

 vision, fine fibres appear around the nucleus in a plane perpendicular to 

 the longitudinal axis of the filament. These fibres, which closely reseml >le 

 the spindle fibres of other plants, are very numerous, and run from the 

 nucleus to the outer limits of the cytoplasm. They are all in practically 

 the same plane, and thus form a plate across the centre of the cell in the 

 place where the cross-wall, between the daughter-cells, is to be produced. 

 At the end of each fibre there is laid down against the cell-wall a small 

 irranule, which stains black with Haidenhain's hrematoxvlin. These 

 granules increase in size until they coalesce to form a ring around the 

 centre of the cell. This ring marks the place where the cross-wall is 

 to be formed, and it can still be seen, around the edge of this wall, after 

 the wall has grown completely across the cell. The author points out 

 that these facts tend to show that the nuclei of the Cyanophycese may 

 have functions similar to those of the nuclei of other plants. The presence 

 of the fibres may indicate paths of conduction from the nucleus to the 

 cell-wall. 



Two Epiphytic Algae.* — J. W. Snow describes two new genera of 

 minute epiphytic fresh-water algas, containing each one species. Pirulus 

 gemmata is recorded from Guatemala and also from Switzerland, grow- 

 ing on liverworts and mosses. In its early vegetative state it shows 

 nothing distinctive, and might be mistaken for a Chlorella ; but in the 

 shape of its adult cell and in its mode of reproduction it is unique among 

 all green algae. The mature cell is pyriform, symmetrical, or irregular ; 

 reproduction is by budding, in which the smaller end elongates and is 

 cut off by a membrane, after which a separation may occur or not. The 

 author compares the fragmentation of the filaments to the similar process 

 in Hormidium, and discusses the possible causes. 



Aeronema polymorpha, the second alga described, also grows on mosses 

 and liverworts, and on flower-pots in greenhouses, and may assume the 

 characteristics of a typical unicellular alga, or may take on the nature of 

 a well-branched filament. The form assumed by the plant is greatly 

 influenced by the concentration of the culture medium. Details are 

 given. The alga reproduces by means of zoospores, which are described. 

 Their mode of germination seems to be the same as that in Stigeoclonium. 

 The genus Aeronema is placed by the author near to Conferva or 

 Bumilleria. 



Gonium pectorale.f — B. SchussDig has been successful in observing 

 the formation of gametes in Gonium perforate. The material appeared 

 in a culture-glass, and was presumably developed from resting-spores. 



* Bot. Gaz., li. (1911) pp. 360-8 (1 pi.). 



t Oesterr. Bot. Zeitschr., lxi. (1911) pp. 121-6 (1 pi.). 



