244 Dr. A.Braun on the Vegetable Individual. 



pletely independent of each other *. The importance of the cell 

 as an individual seems to be decided by these facts ; that of the 

 entire plant, as a superior whole composed of individual cells, 

 seems to be settled, and a firm foundation for the doctrine of 

 vegetable individuality to be gained. But let us try to obtain a 

 clearer view of some of the most important of these facts. The 

 view which regards all cell-formation as a process of reproduction 

 rests upon observations of the formation of free daughter-cells, 

 (blastidia) in the contents of the mother-cells (matrices), — the 

 so-called //'ee, or endogenous, cell-formation. Schleiden, who dis- 

 covered this process, and Karstenf, the most decided and original 

 of his followei's, regarded endogenous formation as the universal 

 law of cell-formation. By this view the whole doctrine was 

 turned in a wrong course, from which it could only be gradually 

 recovered by the discovery, or rather the farther investigation, 

 of another mode of cell-formation, which Nageli designated as 

 " wandstandige," Unger as " merismatic,^^ and Mohl as "cell-for- 

 mation by division of the primordial utricle." But even at this 

 day the misconception caused by generalizing the view that new 

 cells are formed within old ones, has not been entirely removed. 

 I have already J called attention to the fact that cells are divided 

 which have no cell-wall, which is often the case among the 

 Alg8e§. In several genera in which numerous spores are formed 

 in one mother-cell, its entire contents first divide into two parts 

 (the so-called daughter-cells), which, without first secreting a 

 cell-wall, immediately divide again into two; and this process 

 may be repeated over and over |], according to the number of 

 spores which are to be formed (8, 16, 32, &c.). In the second 

 and subsequent divisions there is no formation of new cells in 

 old ones, of daughter-cells in mother-cells, and hence no repro- 

 duction, in the sense of one or more individuals being produced 

 in an old one. The entire mother-cell is converted into two 

 filial cells ; the filial cells are nothing but the mother-cell divided. 

 And this is essentially the case in every cell-formation by division ; 

 for the wall of the mother-cell (within which the division gene- 

 rally takes place) certainly is not the living mother-cell, but 



* Many Palraellacete, Desmidiacea;, and Diatomeae. Cf. Braun, Ver- 

 jiingung, p. 132 et seq. 



t II. Karsten (De Cella Vitali, 1843) emphatically rejects every mode 

 of cell-formation by division and by sprouting, and asserts that every cell 

 originates at its first appearance as a dot-hke utriculus ; regarding all form- 

 ations found in the contents of the cell as cell-brood. 



X Cf. V^erjiiugung, )). 245. 



§ E. g., ProtocuccHS {viridis), Characium, Pediasfrum, Ulothrix, En- 

 teromorpha, Ulvn, &c., during the process of spore-formation. 



II Nageli (Mono(;ellular Alga;, p. 28) calls such cell-generations " transi- 

 tory generations." 



