X69 



Increased elimination ©f water from the exposed cells and 

 tlRBjies comes first of all under conBideration in the forma- 

 tio:ft of wound cork. It ia certain that "wound-cork" can alf?o 

 h© produced Independently of any Injury, if only the elimin- 

 ation of water is in some v?ay abnormally increased. A oaae 

 (188) of thia kine peemB to me to be present when the large celled, 

 thin walled, strongly transpiring inturaepcences of Hibiscus 

 are separated from the normal mother stimctiare by a layer of 

 wound cork . It is v/ell known that wound-cork is formed 

 sooner or later in callus exoresoenoevS, which grow out on 

 the cut surfaces of cuttings etc. It is difficult, to decide 

 whether the formation of wound-cork nhould be considered as 

 a delayed effect of wound-stimuli, or as a result of the 

 strong transpiration, to which the callus tissue is exposed. 

 Similar conditions are present in the intumescences aiown 

 above (fig. 23), the formation of which is preceded by a 

 dissolution of the normal cell-continuity and the foundation 

 of which is often connected directly with wound-cork, In 

 these, as in callus, it does not seem to me Improbable that 

 the abnormally Increawed transpiration of abnormal tissues 

 can call forth the forra^itlon of wound-cork entirely indepen- 

 dently of the dissolution of the tissue continuity and of 

 "wound-stlmull"2 ^ 



Up to the present, it has not been proved iBfinitely 

 that under certain circumstanods factors other than abnor- 

 mally Increased transpiration can also cause the formation 

 of wound-cork; but there is much in favor of it. Wound cork 

 is often produced when separate cells or cell-groups die in 

 the inner part of the tissue; a more or lese Btrong cork 

 mantle is formed arouhd this center of disease. It does 

 not seem to me very probable that the transpiration of the 

 cells left in the center of the tissue has been abnormally 

 increased, and that the formation of wound-cork has been 

 caused by this; ratlier we should not Select the supposition 



that some products of disintegration, produced at the center 

 of disease, have incited the adjacent healthy tissue to the 

 formation of cork. One of Vochting's^ observations favoare 

 this. He often found dead pieces of tissue enclosed in the 



■'• Compaye above p. 86 note. 



2 The production of cork in thd leaves of Rlbes grossu- 

 lar la seems to be comparable with the cases named, in a low 

 lying pa»t of his e xpe rime ntal garden, Sorauer (Handb, d. 

 Pflanzenkrankh, , 2. Aufl., 1886, Bd. 1, p. 222) observed 

 gooseberry bushes with groups of branches entirely gray 

 leavwd, Sorauer designates the disease as cork-sickness. 

 The Individual leaves v/ere either covered only with two cush- 

 ions or cork, spread out like wings, or were coated over and 

 over with cork. I think it allowable to deduce from Sorauer 's 

 stQtements concerning this disease, which I myself have hrd 

 no time to investigate, that the formation of distended in- 

 tumescences precedes the abnormal production of cork - fihe 

 palisade cells stretch and burst the epidermis - then follows 

 the formation of wound cork. 



^ Ueber Transplantation am Pflanzenkorper, 1892, pp. 

 113 ff. The cells connecting directly with the destroyed 

 parts always become cork; "those following next, however, 

 often the majority present, are still unbrowned and of a 

 cellulose nature. This is then retained even if all pro- 

 cesses of growth have long ceased". The ttirning to cork is 

 almost always absent, even "if thickened walls turn brown 

 in the zone of contact and delicate walls occur in the ele- 

 ments belonging to or adjacent to these". If is an open 

 auestion whether these cells also can serve for a covering 



