854 



cross section of a brown wood thread from the sap wood of a very old vine ; 

 j,j,j,j, the boundaries of the annual rings; k, a radial, fibrous crystalline 

 aggregation of calcium carbonate imbedded in the brown gum mass of a 

 broad vessel; the contents of the adjoining wood parenchyma, of the libri- 

 form fibres and medullary ray cells are much browned and those lying 

 nearest the vessels tt, are filled with tyloses. 



Fig. 202, 4, shows a vessel in cross section, the adjoining wood paren- 

 chyma cells from a dead piece of wood lying under the terminal wound of a 

 one-year-old shoot. Besides colorless gum, it contains radially arranged, 

 stem-like aggregations of calcium oxalate. The lower figure is that of a 

 vessel with the surrounding wood parenchyma from the heart wood of a 

 very old grapevine. The vessel is filled with tyloses in which are contained 

 crystalline aggregations of calcium carbonate (after Rathay). 



We have cited this case here because, as typical of many other cases, it 

 proves clearly that the gum formation is the result of wound stimulus and 

 at tlie same time shows how easily diseases may be listed as parasitic, in 

 which is concerned only a subsequent infection by parasites which infest 

 wounds. 



This concerns especially herbaceous, fleshy and juicy organs. In this 

 connection, attention should be called to a work by Spieckermann^ who 

 points out especially the resistance of a cork membrane to bacteria and the 

 necessity of a definite high amount of moisture in the surrounding air as 

 well as the water content of the tissue itself, aside from its specific sensitive- 

 ness, in order to make p()ssil)le bacterial decomposition even on a wound 

 surface. 



The Slimy Exudations of Trees. 



In connection with the relation of parasitic infection to wound surfaces, 

 already mentioned under "Gummose hacillaire," we will mention here the 

 phenomenon where a usually slimy, or gelatinous, and at time clayey looking 

 exudation is noticeable very frequently in different kinds of trees, and even 

 in summer remains moist and variously colored. 



According to our conception of the matter, an excessive bleeding of the 

 trunk is involved here from wounds which cannot heal, Molisch- has 

 proved that a local bleeding pressure makes itself felt in every wound which 

 begins to be overgrown. In consequence of the injury, the cambium, as 

 well as the parenchymatous elements of the wood and bark, is incited to 

 increased activity and cell division. With this is connected such an increase 

 of turgor that water is pressed out of the wound often under enormous 

 pressure (at times, 9 atmospheres). 



1 Spieckermann, A., Beitraf? ziir bakteriollen Wundfilulnis cler Kulturflanzen. 

 Landwirtsch. Jahrbiicher 1902, p. 155. 



2 Molisch, H., tJber lokalen Blutungsdruck und seine Ursachen. Bot. Zeit. LX; 

 cit. Just's Jahresber 1902, II, p. 618. 



