6m BrrA.Braun on the Vegetable Individual. 



plctely iudependent 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 /ree, or endogenous^ cell-formation. Schleiden, who dis- 

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

 of his followers, 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 

 Alga3§. 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 iirst 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 Palmellacese, Desmidiacese, and Diatomeaj. Cf. Braun, Ver- 

 jiinguug, p. l.'32 et seq. ^ . \^..,- ', 



t II. Karsten (De Cella Vitali, 1843) emphatically rejecfs' every mode 

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

 originates at its first appearance as a dot-like utriculus ; rcgai'ding all form- 

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



+ Cf. Veijungung, p. 245. ' * '"' /^J^^'-j; 



§ E. g., Protococcus [viridis), Characium, Pcdiastriim, Vlothrix, En- 

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



II Nageli (Monocellular Algaj, p. ^8) calls jsuch cell-jgeneratio^s^ " trausi- 



