ADDENDA TO BOOKS I. AND II. 571 



originated in the parent-cell, is said to represent the intercellular passage 

 between them. Endosmose of water completely isolates the two secon- 

 dary cells from each other. 



1843. Quekett, in the Microscopical Journal and Structural Record 

 for 1841, ed. by D. Cooper (in the extract in the Botanisehe Zeitung, 

 p. 80.). The primary utricles of the vessels are derived from cytoblasts, 

 which subsequently become absorbed. 



Mirbel and Payen, in the Comptes rendus, January. A globule- 

 cellular substance, the cambium, precedes the formation of cells ; consists 

 of hydrates of carbon, dextrine, gum, sugar, &c., and nitrogenous sub- 

 stances. 



Endlicher and Unger, Grundziige der Botanik. Distinguish primary 

 and secondary cell-formation. The first consists in the development of 

 cavities in an uniform mucilaginous substance. Originally the cavities 

 have no proper walls ; these are subsequently formed particularly in 

 Algae, Lichens ; general in the lower plants, rare in the higher. The 

 second is either intra-utricular or merismatic cell-formation. In the 

 former, the cells are formed, singly or in numbers, from the contents of 

 cells already existing, so that the parent-cells expand and become dis- 

 solved ; especially in the formation of spores and pollen. The latter, or 

 merismatic cell-formation, consists in the division of existing cells by the 

 formation of septa. This kind of cell-formation is the most general. In 

 both the latter kinds of cell-formation it is not the nucleus from which 

 the new cells are immediately produced, but the mucilaginous granular 

 contents of the cell. 



Hermann Karsten, De Cella vitali Dissertatio. The cells originate 

 by the expansion of amorphous granules of organic matter in the 

 cells. 



1844. Hugo von Mohl, Some Observations on the Structure of Vege- 

 table Cells (in the Botanisehe Zeitung, p. 273.). In all vitally active cells 

 a living membrane occurs, consisting of a nitrogenous layer : this mem- 

 brane exists earlier than the cell-wall formed of cellulose, and therefore 

 Mohl calls it the " primordial utricle." The new cells probably originate 

 by the solution of the old primordial utricle, and the formation of several 

 new ones effected through a nucleus, which always precedes the cell- 

 formation. 



Unger, The Growth of Internodes considered anatomically (in the 

 Botanisehe Zeitung, p. 506.). The multiplication of the cells is the 

 result of the formation of septa. The nucleus is a secondary matter 

 here. 



Nageli, Nuclei, Formation and Growth of Cells in Plants (in the 

 Zeitschrift f. wiss. Botanik, B. I. Heft 1.). The opinions are essen- 

 tially those given at pages 33, and 34 II. 



1844. Grisebach (in Wiegmann's Archiv, 134, et seq.). The cells 

 are multiplied by division, without cytoblasts. Appendix to this. There 

 occur 1 . free rudiments of cells, swimming in the parent-cell ; 2. fre- 

 quently free secondary cells,~swimming with these ; 3, cells with parietal 

 cytoblasts, i. e. perfect secondary cells. From this it is concluded that 

 my theory of cell-formation is correct. 



1845. Anonymous, Researches on the Cellular Structures which fill up 

 Vessels (in the Botanisehe Zeitung, p. 225, et seq.). The cellular organs 

 originate in the cavities of old vessels as vesicular protrusions of the 

 neighbouring cells, which penetrate through the canals of the pores, while 

 a nucleus is subsequently developed in them. 



