219 



toward the larval cavitv, the phloein toward the outerside^of the 

 ge.ll, (revoreed aoco^'ding to Beverlnck, in the gall of Aphilo- 

 -vthrlx Malpif^M) , or they .jnsp through the hark of the gall as a 

 delioate network es mav he found in the fleshv pericarp of 

 many fruits, Courchet*^ has explained the double vascular bundle 

 ^J^l ^^ *^^ ^'^'^'^' °-^ pemph igus oornioularia by peculicar processes 

 6f folding and oopleRoencjo In JTTe^br gar bearing the gall. 



5. leyating giseues 



In general, th^ tissues of the galls are even more porously 

 construotef. than aire the likevyise roostly porous callus tissues. 

 Almost every:/here at least small inter6ellular spaoes are dis- 

 tinctly reoognizahie, so that provision of air is assured for 

 the gall tissues and gall occupants. The porous texture of the 

 "b^yk tissue in many Cjmipides galls is very striking. The single 

 cells are provided ";vith long slendter arras, by vhich they are con- 

 neoted with one another;- between the single cells lie extensive 

 (357) intercellular spaces. Figure 118 gives a few cells of this kind 

 Of star-parenohyraa froK the Kollari gall. In other eases, in- 

 stead of star-like cells, elements distended into pouches are 

 formed which are connected witli one another only at their slender 

 ends, or through especially short pointed protuberances. We find 

 the sane conditions in the tissue of bark excrescences and lenti- 

 eel outgrowths;- of the native Diptera galls, that of Diplosis 

 tiliarum . for example, is especially rich in "aerating tissue" 

 of the kind described. 



In the Kollari gall, the Argentea gall etc., the star-like 

 parenchyma cells lignify in the later develppmental stages and 

 take on an abundant pitting. In the gall of Oynips Mayri . 

 cells of rxc Inconsiderable wall thickness are produced. 



The question must remain open as to whether the air -reser- 

 voirs, furnished in these tissues which abound in interstices, 

 can in any way aid the well-being of the gall animals and in so 

 far be termed '* expediently" functioning tissue forms. As al- 

 ready indicated, very similar tissue and cell forms also occur 

 in other kinds of pathological products (for example, bark ex- 

 crescences), in which fro ra the very beginning the question as 

 to toy "purposefulness** is knoii-n to be unfounded. 



TissHes which contain air occur also in other galls. The 

 characteristic v/hite markings of the gall of Andricus guadrilin - 

 eatus are produced by flatly raised ridges, wRich consist of 

 tissue abounding in interstices. The gall of Aulex Hieraoii is 

 traversed raeridionally by tissue stripes which contain air. 



Pneizmat nodes occur in galls in t>^ form of stomata and len-- 

 ticels« In the ^'enclosed" galls, th» stonhta of the normal epi-- 

 dermis are always changefl in so far that they often lose their 

 ability to close., remaining open permanently;- for example, in 

 many Weraatus galls. In t|ye galls of Dryophanta folii. Dr. d lvisa. 

 D r. longiventris . etc., Kustenmacber found that thd guard cells 



Vascular bundle s with abnormal arrangemerit of the phloem 



occur also in correlation-heteroplasmps (p. ,252). 

 1879. 



Etude s, 1, galles prod, i^ar les aphidiene. Hon-cpeilier ., 



