197 



I would like to call attention to the fact that the 

 foisiTintion of "free" galls Is not met with in prosopXasmas. 

 alone. If, hy thf? action of Schlzoncx^ra lanijyera (com- 

 pare aboV3 p, 205), a kataplasnatio v/oody-excrescence is 

 produced, which distende the hark and then splits it, the 

 developrrifsntal procesp is ovidently similar here to the 

 prosoplaamas juot described. Also, other stirauli besides 

 gall atirauli can call forth similarly outgrowing, endogen- 

 ous formations. In the intumescences illustrated in figure 

 20^ on?uy the m^^sophyll increases in this way, finally 

 rupturing the epidermis. 



further reference should be made to the fact that the 

 developmental diffsrenoe, proved between walled galls and 

 medullary galls, is expressed also in the gall products, 

 which arise dnly through growth of the cells without sub- 

 sequent division < gall -hyper trophy ) . In Brineura galls, 

 the gall animT-lJ! aro "walled in" more or less completely 

 by the groring epidermal cells. In the vesicle gall oc- 

 curring often on Viburnum Lantana (figure 43) a tjipical 

 medullary gall is produced by growth of the ground tissue 

 cells. 



The forms of the various medullary galls differ greatly. 

 The elliptical is most frequently repeated. Where leaf galls 

 are concerned, the gall is either visible on both sides of the 

 leaf as oalotte-likr swellings (figure 88) or it is attached 

 ^^ one side by a small, thin stalk. In the former case, either 

 both sides are equally or approximate ^.y dqually developed, as, 

 for instance, in the gall of IJetnatus vesicator . M« VQlJisnerii 

 etc,, or there is prosent a decidt?d dorso-vehtraiity (compare 

 jgigures III and 112). The upperside displays a different form 

 from that of the under siAe, Not infrequently, the d-Assimilar- 

 ity between the upper and und«r sides may be recognized only by 

 considering the anatomical conditions (figures 108 and 93), 

 Next to the elliptical, the spherical form is usual, ( Nematus 

 gallarum etc.). More complicated forms with diverse outgrowths , 

 obris'tructions etc, may be found among the Cynipides galls. 



Although *h6 prosoplasma'S have a peculiar character- 

 istic form, small variations, corresponding to external 

 conditions, are not rare. It seems a matter of course 

 that the form of the gall varies from the usual one, if 

 unfavorable spaeial conditions arrest its development; «• 

 this case abounds in those galls which are developed in a 

 small space, in closely congested groups ( Neuroterus leri - 

 ticular.is etc.) and are thereby united into extensive ' 

 masse g ( cepidpmyia Oomi ) . 



Still more interesting is the fact that many of the 

 galls, c6.pable of developing on different organs, asfsume 

 different forms on different substrata. However, in all 

 the cases known to me., this formal difference i& vdry un- 

 ts^^ essential, Diplosis bqtularia cam infect different parts 



of FraxinuS leaves. If the midribs of the leaflets are 

 Infected, roll-like leaf -foldings are produced, as shown 

 in figure 91A. But if the galls are formed in the leaf 

 axis, the sldnter leaf -blades of the rhachies BweH out 

 into fleshy ridges, which enclose the larvae cavity 

 (figure 91B). The majority of the other gall animsla, 

 however, ( Piplosis tiliarum . Spathegaster feaocarum etc. ) 

 which form their galls on different organs Of tne host 

 plant, always produce the same gall form - with but very 

 slig^ht differences* 



