211 



As an example may he named the gall of Aulex Hieracil; 

 internally each Isrvcl chamber is f ou.-ncl to te s\irroiirrefl hy 

 a hard protecting layer while a richly ^^veloped gall bark 

 lies outside of all. In other galls, the proportion between 

 the gall bark r.nd the "inner gall" varies. In the prodixcts 

 of HormoTOylr. oatjresta . for example, v;hich exists on v/illows, 

 only a vewy few layers of bark tissue lie between the mechani- 

 cal tissue and theopidorrais, 



£, In forms of the second type, the mechanical tissues 

 lie dlrootly bon&r.th tho epidermis , Thc> "gall bar>.", in Bever- 

 Inok's Bonse of tho word, is hnre r-educod to the epidermis. 

 The oft-montionod., undetermined Banisterir^ gall (fig. 93) bears 

 on its upper side a tv70 layered r-H bark, composed of one Igcy^r 

 of opidormis and a lajrnr of palisr.d.: tissue. On tho underside, 

 the mechanical tissue lies directly against the epidermis. 

 Figure 90 illustratos Finilar conditions: merely one layer of 

 epidermis lios above the inochanioal tissue Rone. Further exan- 

 (244) plea are furnished by the leaf-curling gall of the Pistaciae, 

 produced by Paraphigus ppillidus, P. retroflexus and p. semilun - 

 ularius. The gall of Andricus co ri aoeus , abounding on various 

 southern European oaks, consists, "TTt any rate at the time of 

 ripening, onJ.y of ep5.derrQis and tho "inner gall". The mechanical 

 tissues are strongly developed. In the Kollari-gall (produced 

 ^y Cynipa Kollari ) the epidenais is thrown off prematurely, so 

 that the outermost tissue layers of the ripened gall are the 

 mechanical ones. (Beverinck loc, cit. p. 15^); I found similar 

 conditions in the gall of Cynip.s Mayri and Kuetenmacher (lots, 

 cit. p. 181) in that of C. ferruginea . 



3. Ufhe third type is characterized by the f§ct that the me- 

 chanical tissues extend to the outer surface of the gall. Even' 

 the outermost tissue layer^ like those next following, is formed 

 as a mechanical one:- an especial epidermal layer or a "gall 

 bark" can scarcely be spoken of as in Hormomyia fa/^i (fig. 103), 

 Dryophanta divjsa . etc. The outermost laj^-ers' of' "fche mechanical 

 tissue often consist of cells elongated tangentially, those 

 lying deeper of radially oriented ones. In the ask gall of 

 Pi plosiff ootularia . the cells of the epidermis take part in the 

 sclerosis, at least in places (fig. 110). In this, as in the 

 fagus gall, "enclosed" galls occur of which the epidermis is 

 derived developmentally from the normal one. 



The form of the meohanicp-l tissues, corresponds entirely 

 to its significance for the inhabitants of the galls. Speaking: 

 tell^eologically, the question is one of preventing the collapse 

 of the cavity inhabited by the gall animals, of insuring ifs 

 form and of closing the v;ay into the interior to animal enemies. 

 Accordingly, the mechanical gall tissue usually represents an 

 armor, closed on all sides, which in thickness and extent cor- 

 responds more or less to all demands. The question, therefore, 

 whether the firm "mechanical mantel" is only a few. cell layers 

 thick or whether practically the whole gall consists of mechani- 

 cally effective tissues is of no importance for its forPBl 

 character. 



The form of the mechanical mantel usually .-j^ep^at a in minia- 

 ture the form of the whole gall. In spher;M3^Jt galls, we again 

 find the ball form in the mechanical mantel (figure 108A), In^ 

 the flat, elliptical oak-gall (B), of the %^')5iisteria gall (E) 

 of the short -cylindrical gall of pj^.rin^*;luj6 |f igure> 90) etc., 

 the form of raechanicra iriantel always foH,p'\^'S 'kjhfvt of the wh»le 

 gall. She same conditions are present ijfiffiia ^nd walled galls. 

 These do not represent a closed body jS'tiioe ftn Pp^W panp-l unites 

 the larval cavity with the outer wpvia.' ^ mpclianical mantel ifi 



