195 



in the growth. It is therefore ruptured by the strongly pr«- 

 li f editing me sophyll, and a gnll is produced, the outer cover- 

 ing of which - just as that of side roots produced ©ndogensor.s- 

 ^^ ?!. *^® ^^^^ " *°®® "°* ©riginafe development ally, from that 

 of the nori^Rl organ. Figure 87 illustrates a vqt-^ young de- 

 velopmental stage of the gall. On the underside are visible 

 the broad walled edges, by which the larval chamber has been 

 formed; on the upperside, through active growth of a circular 

 roll (na),the epidermis (e) has been pushed up and ruptured, 

 under the covering thus pushed back, a flat tissue head, thick- 

 ly beset with hairs, is produced, through the intensive growth 

 of which the old epidermis already ruptured will later be 

 stripped back and torn off. The greater mass of the nature gall 

 may be traned back to this medial tissue head. With Kusten- 

 macher-*-, we will term "free galls" those which, like the ones 

 here describdd, are not enclosed by normal tissue, or rather, 

 its derivatives, but by a newly formed membrane -tissue. We 

 will return to .these in the next section. 



4, While, in the forms as yet discussed, the gall /inimp.10 

 persistently remained on the upper surface of the plani! organ 

 which produped the gall, or only later, by coalescence of the 

 wall rolls, were enclosed on all sides by tissue masses; - we 

 find in the representatives of the fourth group, that the en- 

 tire development of the gall animal from the very beginning is 

 enacted in the interior of the organs, bearing the gall. 



If the eggs of the future gall -inhabitants are deposited 

 by the mother animal in the interior of any plant organ what- 

 ever and the infected tissues are stimulated to outgrowth, 

 CQmbiaX g^ll? are produced. Representatives of this fourth typo 

 are foiind among Diptera and Hymenoptera galls. 



While in sac galls the abnormal growth took place predom- 

 inantly parallel to the upper surface of the infected plant or- 

 gans and in walled galls the direction of growth was so deter- 

 mined by the egg and the larval body, that the tis8u.e increased 

 most actively tangentically, we cB[n call the radial direction 

 the one preferred in the growth of cambial galls. Round about 

 the larvae or the eggs a large tissue knot iS produced, of a 

 spherical, egg-shaped or elliptical form, which appears as a 

 thickening of the infected stem, or as an embossment of the inft 

 fected leaf, or may be attached to the leaf, stem, root etc. 

 as an independ#nt ^appendage , while the outlines of the organ 

 which bears the. gall would not be essentially altered by it. 

 With liacaza-DuthlerS^ we can call the first kind internal galls, 

 the second kind external ones. That numerous transitional 

 (220) forms are found is directly evident. Further, we will have to 

 distinguish between one and several-chambered galls, as m 

 walled galls.- F6r instance, the galls produced on Salix by 

 nematode species {leaf wasps) contain only one chamber (coni~ 

 pare for example figure 88). The large stem knot galls of Julax 

 Hjeraoii on various species of hawk -weed are many chamberea. 



Further, the difference between "free" and "enclosed" galls 

 (Kustenraacher) deserves especial consideration. In cambial 

 galls it frequently happens that only the tissues which lie in 

 the closest proximity to the egg can increase abundantly,- the 

 cell layers lying abov« participating little or not at an m 

 the outgrowth. The inactive tissues are ruptured by those 



•^ Loo. cit. p» 112, 



^ Rech. pour servir a I'histoire d. gables. Ann. Sc. Uat. 

 Bi>t»* III serie, 186S, T. XIX, p. 273, 



