256 

 tlvely to cross division, has not yet been obderved^. 



It is possible that in the Mar chant iaceae also a 

 similar difference exists between the "epidermis" and the 

 remaining tissue, as in the described higher plants. Ao- 

 oording to Vochting'^ the "epidermis" in contrast to other 

 t:!.SBue forms remains inactive in regenerative phenomena, 

 Rug©^ observed TSudding from the epidermis, 



t. ground Tissue 



■ I n m il" I I ■h i 



'The ground tissue - the oasinilctory as well as the meohaa- 

 ioal^ to naaie its two most lrap<)rtant forma - is espeoir.lly 

 plastic. 



Arresting influences of very different kinds are able to 

 • Buppresfl more or less completely «ii processes of differentia- 

 tion, to decrease the normal cell- nxiiBbsr nnd to prevent the full 

 maturing of the indlcidual oelis (size, development, thickening 

 of the membrane, formation of ohlorophyll etc.). The oelXs of 

 the ground tissue are shown to be in ©very waj*' extraordinarily 

 Busoeptible, 



Favorable influemoes call forth in it hyperhydrio, callus 

 or gall hypertrophies in which, the cells of the ground tissue 

 can grow out into great pouches ^nd vesicles. So fay as Its 

 oapacityfor cell division is concerned, the ^ound tissue is 

 greatly superior to the epidermis, Sails espeoially demonstrate 

 that the cells of the mesophyil, of the bark eto, are capable 

 of extensive division In all d.-fiec tloiis, the products of which 

 can undergo most diverse dif farentiatj.on. The ground tifssue 

 (298) also pr.rticl pates greatly in ths forma clon of callus tissues and 

 Is constantly livelier In its aotionothan is the epidermis* 



However, all the layego of the ground tissue in the same 

 trgfn do not participate equally in the construction of abnormal 

 outgrowths. In the window galXs of the maple (fig, 4S) the up- 

 permost cells of the raesophyXl often remain unclian^ed, whi:*.© the 

 cells of the other layer are greatly enlarged. The same holAs 

 good for the Banisteria gall illustrated in figure 93, in which 

 the upper palisade layer remains normal » while the cells of the 

 lower layers divide extraordinarily actively. In leaves infec- 

 ted by fungi, the cells of the spongy parenchyma are at 'times 

 predominantly Incited to division. In many oilier galls, the 

 different layers cf the mesopfcylll behave differently, yet the 

 differences are not so strikfjigiy noticeable as those in the 

 cases first named f compare, for example, fig, 104). In intumes- 

 cences the cells of the upper.nost or undex*most layer are often 

 the only ones abnormally elongated, alt hough we find in cases Of 

 "severe" sickness, that all the layers are similarVy changed. 



■^ In the fornr-tlon of a dventitious sho ots, cross-division 

 takes place in the epidermis of various plants. . As the best 

 known example, the adventitious shoots of begonia leaves may be 

 named here, which are knov/n to be outgrowths of single epidermal 

 cells, 



2 



Ueb. d. Regeneration d. Mar chant iace en, Prlngsheio's 

 Jahrb. f, wiss. Bot, 1885, Bd, XVI, p. 367. 



3 



Beitr, z. Kenntnis der Vegetationsorgane der Lebermoose, 

 Flora 1893, B4, 3;XXVI1, p. 279. 



