ZOOLOaY AND BOTANY, MICROSCOPY, ETC. 227 



Plurality of Cotyledons in Persoonia.* — Baron F. von Miiller 

 states that in twenty-three out of the sixty-one Australian species of 

 Persoonia (Proteaceee) there are more than two cotyledons, the number 

 varying from three to six. The only previously known example of a 

 plurality of cotyledons among angiosperms is in the genera Loranihus 

 and Nuytsia of Loranthaceae. 



Division of the Nucleus and of the Cell.f — In his most recent 

 publication on this subject, E. Strasburger describes the mode of 

 division of the nucleus, and the relation of this to the mode of divi- 

 sion of the cell itself in the pollen-mother-cells and endosperm of 

 various monocotyledons, especially Liliifloree and some dicotyledons, 

 the staminal hairs of Tradescantia, the tissue-cells of Asparagus and 

 Hyacinthus, the vegetative cells of Ghara, Spirogyra, and CEdogonium, 

 and in some animal cells. The investigation was made chiefly with 

 preparations in alcohol-sassafran and acetic-acid-methyl-green. 



The differentiated parts of the living protoplasm Strasburger 

 distinguishes as cytoplasm (the cell-protoplasm), nucleoplasm (the 

 nuclear protoplasm), and chromatoplasm (the protoplasm of the colour- 

 ing and allied substances). Each of these three modifications is a 

 compound of a hyaline matrix or hyaloplasm, and of imbedded 

 granular structures or microsomes ; so that, by a combination of these 

 terms, we may speak of cytohyaloplasm, nucleohyaloplasm, cytomi- 

 crosomes, &c. 



The resting cell-nucleus consists of nuclear substance and nuclear 

 sap. The whole of the former is composed of a single very long 

 thread of nucleoplasm, twisted here and there into knots, and 

 suspended in the cavity of the nucleus filled with watery nuclear sap. 

 Towards the cytoplasm this nuclear cavity is shut off, like an 

 ordinary vacuole, by a membrane, the wall of the nucleus, which 

 belongs therefore to the cytoplasm. The nuclear filament consists of 

 a matrix of nucleohyaloplasm with nucleomicrosomes imbedded in it. 

 These latter are distinguished from the cytomicrosomes by their 

 different capacity for receiving colour with specific pigments. The 

 author does not agree with Flemming's description of the nucleus as 

 composed of chromatin and achromatin. Among the nucleomicrosomes 

 are included the nucleoli, which are distinguished from the rest only 

 by their size. 



When the nucleus is preparing for division, the nuclear filament 

 first of all contracts, decreasing in length, but increasing in thickness ; 

 and the microsomes coalesce into larger granules. Finally the filament 

 consists of alternately denser and less dense plates of microsome- 

 substance and hyaloplasm. The nucleoli disperse into the substance 

 of the filament. The filament now either becomes at once segmented 

 into distinct pieces, or this segmentation takes place later. In the 

 first case the separate pieces, which are attached to the nuclear wall, 

 lay themselves side by side, so that the free ends somewhat diverge. 



* N. Zealand Journ. of Sci., 1882. 



t Archiv f. mikrosk. Anat., xxi. (1882) (3 pis.). See Bot. Centralbl., xii 

 (1882) p. 259. 



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