34 ON THE PL ANT -CELL. 



the mother cells, and which last subsequently disappeared first. I find 

 it, in fact, impossible to obtain such a section as is represented by Unger 

 (table v. op. cit.). 



There often appears on the free side of the cytoblast, as, for instance, 

 in the Fritillaria imperialis and in Chamcedorea Schiedeana, a new 

 lamella, which, at the edge where it touches the cytoblast, combines 

 with the first cell wall, and thus encloses the cytoblast. Such cytoblasts 

 seldom undergo any further change. The cytoblast, after the formation 

 of the cell, sometimes becomes absorbed, and sometimes remains for the 

 entire life-time of the cell. The cell at first consists of jelly (gallerte), 

 and easily dissolves in water ; gradually it becomes changed into cellulose. 

 I have traced accurately the steps of this change in the albumen of 

 Leucojum cestivum, Phormium tenax, Colchicum autumnale, Chamce- 

 dorea Schiedeana, Pedicularis palustris, Momordica Elaterium ; in Lu- 

 pirnts, and many other Leguminosce ; in the embryo sac of Alisma 

 Plantago, Sagittaria sagittcefolia, Pedicularis palustris, CEnothera eras- 

 sipes, Tetragonia expansa ; in the germinating cotyledons of Lupinus 

 tomentosus ; in the many-celled hairs of Solatium tuberosum, and 

 many other plants ; in the sporangia of Borrera ciliaris ; and in the 

 sporocarpium of Blechnum gracile. 



II. In addition to the above mode of cell-formation, Niigeli has de- 

 scribed a second, which he first observed in the formation of the primitive 

 cells of the pollen, and has more recently found to exist in a large 

 number of A/ace. Mohl imagines something of the same kind to take 

 place in the new cells of the cambium. To this mode of cell-formation 

 belong all those cases where the division of cells takes place. I have 

 not had an opportunity of making any observations on this subject, but 

 the following facts are after Nageli : 80 long as a cell is internally 

 covered with a layer of mucus, this process may go on. In the first 

 place, this mucus layer is divided into two or four parts, each of which 

 is surrounded by a delicate layer of mucus. These external mucus 

 layers are converted into cellulose, and thus two or four little sacs or 

 cells are formed, which perfectly fill up the primitive cell. In a 

 peculiar and hitherto unexplained way, the cytoblast seems to be very 

 active in this process. This increase takes place in most instances in 

 cells with a central cytoblast, and this divides itself into two or four 

 cytoblasts, each of which becomes the central point of a new cell. No 

 objection can be made to this history of cell-formation founded upon such 

 careful observations. Of the part it plays in the vegetable kingdom 

 Niigeli has given the following account. It seems to be the only mode 

 of cell-formation in the Diatomacece, Nostochinece, OscillatorietE, Ba- 

 trachospermecE, and Fucacece. In the Conferva it takes place in all the 

 cells except those of the spores. It also takes place in the special 

 mother-cells of the tetrasporous plants, as the Floridece, flepaticcc, 

 frondose Mosses, Ferns, Lycopodiacetz, and Phanerogamia. In the Fungi 

 and Lichens, in the Ulvacece, and in the formation of the spores of 

 Characece and Equisetacece, it is at present unknown. On the other 

 hand, with the exception of the special mother-cells, it is not found in 

 the cells of the Characece, Equisetacece^ Floridea, Hepaticcc, frondose 

 Mosses, Ferns, Lycopodiacete, and Phanerogamia, in all of which 

 the cell-formation takes place around a central nucleus. Probably, 

 further observations would bring this process under the same general 

 law as the preceding. 



Imperfect Observations. There are some cases where the cells are very 

 small and delicate, and nearly filled with granular contents, and where a 



