206 



histology. For the present consideration, it is immaterial 

 whether the epidermis of a eall is derived developrnentally 

 from the normal one, as in "enclosed" galls, or is to be con- 

 crived of as a new formation, as in "free" galls. 



In sac and Faiied-gsills the outer epidermis is composed 

 mostly of 3*olatively large, but often very flat cells, which " 

 are provided with only a moderately strong cuticle. At times, 

 a many Ir^yered epidermis can be formed from one which, under 

 normal conditions, would have only one layer. Isolated crcss- 

 dlvisions may be found in various galls (see above), but such 

 a taig'JQ.ty epidermal sheot as that found in the Diptera gall on 

 OXraus'- shoxm in figure 99 is rarely produced. Here and there 

 eight, t^n and more epidermal cells lie on top of one another. 



The external galls (lacaza-Buthiers galles externes) 

 which appear attached as special appendages to the organs bear- 

 ing them, at tines produce as mr.ny layered epidermis and often 

 sh0T7 a strong cuticle &n their o^ter walls, In the ("enclosed") 

 gall of Memat us gallartim . the cells are rather small and strong- 

 ly out icular i. 'i e d , i compar e figure lOOA), in the gall of Andrious 

 quad gil inert tus they are distended like papillae and have rather 

 'Elilok walls, TFlg» LOOB). In a Californian Cynipides gall on 

 Q uerouB T7islr: aQni. the outer walls of the epiderrap.l cells and 

 the upper pari 51 the side walls are thickened, so that an ap- 

 proximately conical oell-lumen remains fjree (compare fig, 114). 

 The gall of Acr aspls itiacropterae (figure 106) has thick-walled 

 epidermal cells, with ot 1 1.^:63 a pit-like wall structure. 



I tfound a very singular epidermis in a gall of Jacquinia 

 S ohliodean a Mez. The inflorescence stalks swelled out to 

 ^iok, turnip-like bodies, the covering tissue of which is shown 

 in figure 101. The cells in the outermost layer can not, for 

 any length of time follow the gall's continuous growth; they 

 are pressed into sheets, their walls are constantljr drawn out 

 thinner ajid finally tear apart. At the same time, the cells of 

 the lajrer lying immediately beneath this, one assume the funo- 

 (236) tions of the epidermal tissue, since their outer trails are 



great3l,y thickened and powerfully cuticularized. Even the third 

 9.^d fjBJif th cell layers can be transformed in this way. In the 

 figui?il,'flt a, is showp the overlapping of the wall-tbi<Jkening 

 ajid otf J(;jh9*'*p?oc©s8 of cuticularization in the cells*^^ lying 

 deeper. 



So far as I know, cork as a covering tissue is on© of th» 

 rarities in galls. It Is formed comparatively luxuriantly in 

 the gall of Ueuroterus nuraismatis (On Quercus), the character- 

 istic form of which is shown in figure 102a, In the central 

 depression on the dorsal part of the gall are formed several 



Schlechtendal's Verzeichnis, Nr. 361, 



So far as my slight teats permit of a decision, a simi- 

 lar epidermal substitution does not take place on normal axil- 

 lary parts of Jacof Uinia Schiedean a. Sclerdder (System. Anat. 

 d. Dikotyl., pT^lTf) mentioned a subepidermal formation of cork 

 in Jacquinia. Damm has announced recently that the cells of the 

 bark parenchyma in varioiis plants form cuttcular layers and 

 cause the production of a "cut icular epithelium" (Ueb, d.„Bau, 

 dia Entwickelungsgesch, u, d, mechan. Bigenschaften mehrjahr. 

 Epidermen bei d. Dikotyl. Beih. z. Bot. Cbl. 1901, Bd. XI, p. 

 219. Cuticular epitheliiim may be proved in various Viscoideae, 

 A new example is illustrated liy the gall treated of in the text. 



