REPRODUCTION AND REGENERATION 167 



SECTION 47. Reproduction and Regeneration. 



During the progress of development the plant not only reproduces the 

 characters of its ancestors, but also needs to replace such temporary organs 

 as leaves, bark, and root-hairs, while the internal life of each protoplast 

 involves perpetual destruction and reconstruction. When missing organs 

 are replaced by new formations, or by the outgrowth of new primordia, 

 we may speak of reproduction, and restrfct the term ' regeneration ' to cases 

 in which an organ replaces a portion of itself which has been removed l . 



We are not concerned with the details of the remarkable reproductive 

 powers possessed by plants, or the way in which these often lead to various 

 modes of vegetative multiplication 2 . Plant-organs often give rise to 

 dissimilar growths to replace missing parts, and to denote these Loeb 

 has used the term heteromorphoses. Thus buds may arise from separated 

 roots, leaves, or even fruits, protonemata from pieces of the leaves or 

 sporogonia of mosses, which under normal conditions would not be the case. 



Reproduction is possible only by cells which retain their embryonic 

 character, although a negative result does not always indicate the absence 

 of embryonic cells, for the conditions may be such as to prevent their 

 exercising their powers of growth. Nor will the microscope reveal this 

 property, for many cells which appear to be adult retain their embryonic 

 properties. 



Each adult cell of the mycelium of many fungi is capable of reproducing the 

 entire organism 3 , and to a more limited degree the same power is possessed by 

 the cells of the thallus of Marchantia and Lunularia *. All, or a part, of the leaf- 

 cells of mosses may be capable of producing protonemata, and hence new plants, 

 but usually this only takes place in separated leaves 5 . It is quite possible that the 

 protoplasts of other cells are embryonic, but that their cell-walls are incapable of 



1 Cf. e.g. Frank, Krankheiten d. Pflanzen, 2. Aufl., 1895, Bd. I, p. 90; Hertwig, Zelle u. 

 Gewebe, 1898, II, p. 179; Delage, L'her^dite, 1895, p. 92. Goebel (Organography, 1900, I, p. 42) 

 uses the term 'regeneration' to apply to all cases of repair; Delage distinguishes between regular, 

 normal, or physiological and accidental, abnormal, or pathological regeneration and reproduction. 



2 Frank, Krankheiten d. Pflanzen, 2. Aufl., 1895, Bd. i; Vochting, Organbildung, 1878,!; 

 1884, II; Transplantation, 1892, p. 145; Wiesner, Elementarstructur, 1892, p. 99; Rechinger, 

 Verb. d. Zool. Bot. Ges. in Wien, 1893, p. 310; Tittmann, Jahrb. f. wiss. Bot, 1895, Bd. xxvn, 

 p. 164; Massart, La cicatrisation chez les ve"getaux, 1898; Goebel, Organography, 1900, I, p. 41. 

 On adventitious growths cf. Hansen, Vergl. Unters. iiber Adventivbildungen, 1881 ; Beyerinck, Ueber 

 Wurzelknospen u. Nebenwurzeln, 1886; Wakker, Bot. Centralbl., 1887, Bd. XXXII, p. 238; Noll, 

 Landw. Jahrb., 1900, Bd. xxix, p. 395 ; Heinricher, Ber. d. Bot. Ges., 1900, p. 112 ; J. Palisa, ibid., 

 1900, p. 398. 



b Klebs, Jahrb. f. wiss. Bot. 1900, Bd. xxxv, p. 180. 



* Vochting, Jahrb. f. wiss. Bot., 1885, Bd. xvi, p. 367; Schostakowitsch, Flora, 1894, 

 Erg.-bd., p. 350. 



5 Heald, Gametophytic Regeneration, Leipzig Diss., 1897 ; Correns, Ber. d. Bot. Ges., 1898, 

 p. 22 ; Unters. iiber Vermehrung d. Laubmoose, 1899, p. 339. 



