1S4 Prof. H. Karsten on the Formation, 



striam 10. et rnarginem usque ad apicem), basi quoque (a scutello 

 ad humeros) flavo 5 corpore subtus, pedibus antennisque nigris. 



Long. Corp. lin. 2| ; lat. lin. 2. 



A species which may at once be recognized by its four flavous 



bands, each of which is broken, and, as it were, overlaps itself 



medially. 



From the Chevrolat collection ; received from the Cape of 



Good Hope. 



[To be continued.] 



XIII. — Histological Researches on the Formation, Development , 

 and Structure of the Vegetable Cell. By Prof. H. Karsten. 



[Continued from p. 36.] 



§X. 



Formation of new joint-cells by the internal development of tertiary cells, 

 and of the daughter cells contained within the secondary cells. — Folds 

 in the wall of the mother cell. 

 In the different species of the genus Spirogyra the distinctness 

 with which the changes just described as undergone by the 

 endogenous cells may be recognized is very variable, and it ap- 

 pears even to differ in the same species at its different periods of 

 development, or under different conditions of nourishment. 



Although I observed a great number of Spirogyrce, it was 

 especially in S. nitida and S. orthospira that I saw the development 

 of the nuclear cell of which I shall here endeavour to give a 

 general picture ; and although this may be subject to modifica- 

 tions in detail for the different species, or their particular condi- 

 tions of development, it nevertheless gives the certain result 

 that in these plants also the cell-multiplication is effected by 

 endogenous cell -formation, as indeed was to be expected. 



If we trace, in the first place, the changes which are to be re- 

 cognized in the cell-nucleus with its daughter cells, we have in 

 the developmental condition represented in Plate VII.* fig. 85 

 an indication of the production of the septum in the mother cell 

 by the flattening of the two daughter cells which enclose the 

 nucleus of the mother cell between them. 



The further development of this cell-system takes place usu- 

 ally as follows : — Simultaneously with the absorption of the 

 nucleus of the mother cell new cells are produced in the daughter 

 cells ; the latter expand either in breadth, and then in the region 

 of their central, contiguous and flattening walls, or in length ; 

 and at the same time their mother-cell membrane (the original 

 membrane of the nucleus) seems gradually to disappear. The 

 new nuclei of the two daughter cells are situated on their walls 

 * The Plate here referred to will be found in the June Number. 



