x09 ' 



th« epidermal cells 02; the upper side also to the phenomena 

 of growth here descrihed. In this case corresponding areas 

 on both* sides of the colonized leaf are covered with Erineum 

 turf (compare fig. 38). This action on the side of the leaf 

 opposite to the surface ;>rim4rily stimulated seems t6 he corns 

 evident ev'^pecially abundantly on the leaves of Tilia, on v*.ich 

 Prank liad rli-eady foimd ohem. I observed the same phenomenon 

 on the rough, upper leaves of the linden inflorescence. If 

 re overlook the cases in which nesophyll cells also r.re incit- 

 ed to Q weakened g»0".Jth, -.m nrjr a^iswae thr.t, in the forrar.tion 

 of Erinea, those poisons are active. :7hioh incite only the 

 epiderrr'.l cells to intensive grovrth . 



Microchomio methods, mrJ^in^ possible the proof of 

 the sprer.d of gall-poison in the plant body, are not at 

 (116)^ our disposal. u(i can recognize its diosmotic distribution 



orly in itseffeots on the cells of the host plant. As 

 noted above, the eylindrlocil hairs of the Erineum galls 

 form thickly closed masses, ^Inch each single epidermal 

 cell grows out into a hair, The assumption that the gall 

 mites work so exactly and infect each cell separately is 

 less probable tban the one that the poisonous substance 

 given out by them can diosmftse from one cell to another, 

 The hair formations on the side of the leaf not infected 

 support :th is asBuription. On the other ho-na the Erineura 

 hairs are isolated" lf~"clu"6>-"lTke'gi' musteo om-'i'ife^" fi^titf^ 

 are involved. The possibility that for each individual 

 hair an especial act of infection is necessary may be con- 

 sidered here, and also that the poisonous substance of the 

 mites can not diosraose from one cell to another, or at 

 least not in a sufficient amount. To m^ kno\;ledge, there 

 is no case knovm in which mush#6cm-like Erineura hairs had 

 been formed on the side of the leaf not infected, 



"The question as to whether me' epidermal cells en aax psr^rg 

 of plants have this capacity for transformation may be ans- 

 wered only incomnletely by a consideration of the materials 

 offered in nature. Apparently a Jl parts of the plants bearing 

 Erinea, which are above ground, are capable of forming ab- 

 normal trichomes, so long as a living epidermis is present on 

 them. To be sure most of the Erineum forms are found on 

 leaves, but if the mites colonize on young petioles or parts 

 of the stalks, the hypertrophies described are produced on 

 these also. Most of the Erineura forms prefer the underside 

 of the leaf, in the case of Fagus, Tilia, Prunus Padus and 

 others„however, Erineum hairs occur on the upper side also. 

 Cuboni^ observed Erineum turf on bunches of grapes. Further, 

 in many blossoms galls^, trichomes often develop which cram- 



■'■ Compare Kiister, Cecidiol. Kotizen I. Flora, 1902, 

 Bd. XC, p. 67. 



^ Le staaioni speriraent, agar, ital, Roma 1888, p. 5S4. 

 Quoted from Prank, loc. cit, p. 49. 



^ Compare also Molliard, Cecidies florales. Ann. So. 

 lint. Bot. e^^ ser,, 1895, T. I., p/ 67. 



