REPRODUCTION AND REGENERATION 169 



at the extreme apex, none in the older parts, and partial regeneration in the regions 

 between l . Similar results were observed by Lopriore on split apices of shoots 2 , 

 which apparently are able to reproduce the extreme growing apex when it has 

 been removed by a transverse section. Beyerinck has in fact observed the 

 regeneration of a bud cut away from Salix amygdalina*. 



A leaf can apparently develop normally even when a portion of the primordium 

 has been removed, for considerable regeneration occurs when the half of an 

 already enlarging primordium is cut away 4 . Raciborski also observed a regeneration 

 of the forcibly removed apices of the leaves of certain Asclepiadaceae 6 . As in the 

 case of a leaf, when a fern prothallium is sliced in two longitudinally, the symmetry 

 is not restored in the older portions, but only in the new growths formed from the 

 regenerated growing apex 6 . The thallus of Lunularia and of Marchantia behaves 

 similarly, although the cells at the cut edges of the older parts have actually an 

 inherent power of reproducing the entire thallus 7 . 



In certain of the above cases a new epidermis was regenerated, and other 

 instances of this have been observed by Massart (1. c., p. 55), while it takes place 

 normally when the leaves of palms split into segments (Massart, I.e., p. 29). Often, 

 however, and especially in adult organs, no regeneration of the epidermis is possible, 

 but instead it is replaced by cork or similar tissue 8 . A regeneration of the 

 piliferous layer of roots has been observed by Ewart to take place in roots in which 

 the outermost layers had been killed by immersion in a solution of permanganate 

 of potassium, but this occurs only near to the growing apex 9 . Miehe has also 

 observed a regeneration of the epidermis on the leaf of Tradescantia . Living 

 epidermal cells are able to replace the cuticle when it has split off, and a similar 

 replacement may occur in the cells of algae. 



The pileus of Coprinus stercorarius can be replaced by the growing stipe, 

 if the former has been removed n , and the growing sporophores of various other 

 Hymenomycetes are able to repair small defects or injuries. Similarly a broken 

 filament of Vaucheria is able to form a new growing apex at the point of injury, 



1 Lopriore, Nova Acta d. Leopold. Acad., 1896, T. LXVI, p. 211; Ber. d. Bot. Ges., 1892, 

 p. 76. 



2 Lopriore, Ber. d. Bot. Ges., 1895, p. 410 ; Schilberszky, Ber. d. Bot. Ges., 1892, p. 424 ; Kny, 

 Bot. Ztg., 1877, p. 519 ; Beyerinck, Bot. Centralbl., 1883, Bd. xvi, p. 231. 



3 Beyerinck, Wurzelknospen u. Nebenwurzeln, 1886, p. 121. 



* Lopriore, Ber. d. Bot. Ges., 1895, p. 411; Beyerinck, Bot. Centralbl., 1883, Bd. xvi, 

 p. 232. Other leaves, including those of mosses, have, according to Massart (La cicatrisation, 1898, 

 p. 23), little tendency to regeneration. K. Muller's statement as to the regeneration of the leaf of 

 Bryum Billardieri is to be accepted with caution. According to circumstances, splitting the primor- 

 dium of a leaf results either in the complete regeneration of each half or in the production of two 

 half-leaves. Half-embryos as observed in animals are less easily produced by the division of a few- 

 illed plant germ, for the individual cells are so readily capable of separately producing new plants. 



5 Raciborski, Flora, 1900, p. 10. 



6 Heim, Flora, 1896, p. 349. 



7 Cf. Vochting, Jahrb. f. wiss. Bot., 1885, Bd. XVI, p. 367. 



8 See also Tittmann, Jahrb. f. wiss. Bot., 1895, Bd. xxvil, p. 150. 



9 Ewart, Trans. Liverpool Biol. Soc., Vol. VIII, 1894, p. 245. 



10 Miehe, Flora, 1901, p. 131. 



11 Brefeld, Unters. iiber Schimmelpilze, 1877, Heft 3, p. 69 ; Grantz, Einfluss des Lichtes auf 

 Entwickelung einiger Pilze, Diss., 1898, p. 23 ; Massart, La cicatrisation, 1898, p. 18. 



