ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 925 



Characeae. 



Cell-division of Characeae.* — A. Cagnieul has investigated the 

 mode of cell-division in the cells of Nitella intricata and opaca, and 

 does not agree in all respects with the observations of Johow.f It is 

 true that in the cells of the internodes the division of the nucleus takes 

 place by simple constriction, but this is never followed by actual cell- 

 division. It is difficult to interpret in the same way the mode of division 

 of the nucleus in the terminal cells of the stem and branches and in the 

 nodal cells. In the mother-cells of the antherozoids the division of the 

 nucleus can be followed with great ease. The increase in length of the 

 filament composed of antheridial cells is always much more rapid than 

 the multii^lication of the cells themselves, from which it results that 

 the longer axis of the cells is always very long in young antheridia, very 

 short in those that are nearly mature. The nucleus has a very evident 

 nucleolus, and after the application of reagents (chloride of mercury, 

 picric acid, osmic acid, pigments, &c.), a moniliform filament of chro- 

 matin is seen. When segmentation is commencing and the nucleus 

 is dilated, the filament of nuolein, now visible without the use of re- 

 agents, is sharply divided into fragments. Soon afterwards the 

 nuclear plate is formed, and from this moment the spindle of segmen- 

 tation, composed of a very large number of filaments of achromatin, 

 is very clear. This spindle is almost always directed towards one of 

 the diagonals of the optical view of the cell. In the next stage the 

 cell-plate divides in two ; and the two halves, composed of filaments 

 curved into the form of a V, are directed towards the poles of the 

 spindle ; this latter at the same time turning on itself to an angle of 

 30° or 40°, until its axis coincides with that of the cell. The nuclear 

 plate is soon formed, and a nucleolus makes its appearance in each of 

 the newly formed nuclei. 



Fungi. 



Phosphorescent Fungi,| — F. Ludwig has examined under the 

 spectroscope the light given ofi" by phosphorescent fungi, especially 

 Trametes pini, Arjciricus mellens, Xylaria hypoxylon, Collybia tube' 

 rosa, and Micrococcus Pjiugeri, aud finds its spectroscopic character 

 to differ in different species. He maintains that the spontaneous 

 phosphorescence is equal in intensity by day and by night. 



Parasitic Hymenomycetes.§ — According to H. Mayr, the two 

 species of Polyporus found commonly on birch-stems, P. hetuUnus and 

 P. Icevigatus, are true parasites, the mycelium which springs from 

 the spores having the power of jienetrating uninjured living cells and 

 turning their contents brown. The mode in which this parasitism is 

 effected is described in detail in both species. The author describes 

 the singular phenomenon that when both parasites attack the same 

 stem, a solid dark-brown hard division-wall is formed, separating the 

 two entirely from one another. 



• Bull. 8oc. Bot. France, xxxi. (188^) pp. 211-3. 



t S(o llii.s Journal, ii. (1H82) p. 79. 



X Ziilsclir. f. Wi.'iH. Mikr., i. (18H4) pp. 181 08. 



8 Bot. Ctntralbl., xix. (1881) pp. 22-9, 51-7 (2 ply.). 



