170 



clcatrizntionB of the "beftts upon which he operated; but cork 

 had he en formed Only in the vicinity of those enclosures which 

 hr,d turned hrown, in which therefore some products of disin- 

 tegration hr.d heen produced. In different succulents which 

 showed an especial "tendency" toward a vigorous formation of 

 (189) wound-cork after Injury, I repeatedly observed stronglv de- 

 veloped formations of cork in the region of dead parts' of 

 tissue, and, as I suppose, undar the influence of unknown 

 chemical combinations,, In this connection belong perhaps 

 the "cork excrescences" studied by Baohmann'^-, whioh moke- pos- 

 sible the -iroduotlon of extensive tissue protuberenoes or which 

 In places oan channel the organ concerned or completely per- 

 forate It, (Ilex, Zamia, Rusous etc.) while division of the 

 parenchyma cells and the suberlzatlon of their products of 

 division progresses further and further Into the Interior of 

 the leaf. Histologically and ontogenetloally the cork ex- 

 crescences described and Illustrated by Baohra?inn correspond 

 throughout with typical wound cork. 



The manuals of phytopaj^hology should be consulted 

 on potato scurf or scab, Wobbe produced oork excres- 

 cences on potato tubers by cultivating them in water^, 



Silke callus (see above), wound cork ean be produced also 

 on "physiological" wounds. Many plants develop it, for ex- 

 ample, on their leaf soars^. 



5. Galls 



We have termed gal l-fasrmat ions all abnormal tissues pro- 

 duced by the action of vegetable or animal parasites. The 

 great majority of these arise either through ce^.! growth 

 alone (gall-hypertrophy) or through ceil oEivision (gall-hyper- 

 plaeia); Since, in the latter case, the newly produced tis- 

 sues differ more or less- strikingly from ijormal ones, we are 

 concerned only with hyteroplasms in such gall -for mat ions. 



The number of heteroplastically constructed galls is ex- 

 traordinarily large; even the diverse gall hsrper trophies re- 



,^ Ueb. Korkwuchertingen auf Blattern. Pringsheim's Jahrb. 

 f. wiss. Bot,, Bd, XXI, p. 191. 



^ Die Kartoffel als Wasserpflanze, Landwirtsch. Versuche- 

 Stat., 1864, Bd, VI, p. 57, 



Compqire further Tison, Rech. s. la chute d. feuilles d. 

 Dicotyl, These, Caen, 1900. This tissue becomes of interest 

 for pathological plant anatomy only when it arises at the 

 wrong time as a result of abnormal conditions. I would like 

 to refer at this opportunity to the fact that the " tissue of 

 separation ", whioh makes possible the' freeing of the leaf from 

 the axis , "is produced prematurely if the leaves are robbed of 

 their blades; the axis then lets the petioles fall off. Th3 

 question whether the results of wound stimuli are to be recog- 

 nized in this needs siippiementary testing; it is more probable 

 that the reduced t ranspiration determines it; a5.so branches' 

 left in raoipt air are known to drop their leaves. (Wiesner, 

 Untersuch. uber die herbstliche 'Entlaubung d. Holzgew. Sitz- 

 ungsber. Akad, Wiss. Wien„ 1871, Bd. LXIV), In these and sim- 

 ilar cases, the wound produced by the fall of the leaf rls no 

 longer a "physiological" one. The question as to whe'ther the 

 tissiie ^f separation produced on mutilated leaves and by ac- 

 tion of moist air corresponds with the normal one, needs 

 supplementary testing. 



