182 



the form of green ©mergences on the leaves of Crataegus oiqr- 

 aoantfia (after colonization by Ceci donyia Orataegi) may also 

 he include a. here. ' ^~ -^^ 



The vascular and mechanical tissues undergo the same re- 

 duction in kataplasmas as does the assimilatory tissue. The 

 vascular bundles in the parts infected are often only of very 

 moderate extent; the single ducts often retaining the narrow 

 lumina. The mechanical tissues, v;hich under normal conditions 

 protect the vascular bundles, are not developed (compare fig. 

 74). According to V/akker (loc. cit.) the collenchyma is lost 

 in the infected stalks of Vacciniua Vitis Ida ea ( Exobasidium) 

 in the stalks of Rhamnus fran^-ula f Aeoidium aEamni ) and 

 Crataegus oxyaoantna (Roestella lacefa^a H In the same cases, 

 tne scierenchyma also is lacking. 



Finally, the hyperplastic excrescences of the pith should 

 be mentioned. One especially conspicuous forn is found in 

 those produced b y Aecidium Englerianui s on clematis branches; 

 parenohym atous cone-like protuberances are developed from 

 the pith which break through the ring of vascular bundles and 

 the bark.-*- 



While in prosoplasmas all the cell divisions or at least 

 the first ones, accompanying the formation of the gall, often 

 Show a definite orientation and produce regular cell rows, 

 in kataplasmatic excrescences of the primary tissues regularly 

 oriented cell rows are almost entirely lacking. 



In very different kinds of galls, as in wouM tissue (see 

 above p. 166) bead-like structures occur on the outer surface 

 of the cell-membrane, but nothing positive has been discovered 

 as yet concerning their chemical composition. ^ 



2. Secondary Tissues. 



Of the secondary tissues, only the products of the cambium 

 come under our consideration. In the formation of galls, eith- 

 er the living derivatives of the annual ring already formed 

 are incided to division, or its own cells are used in the pro- 

 duction of the kataplasmatic tissue; as described above in 

 the formation of wound-wood. After infection with different 

 fungi or after colonization by gall- animals , swellings are 

 ^ produced in wood and bark usually knob-like in form, or clue- 

 I tered (compare fig. 7 6) , which resemble the canker formations 

 Il208) produced after injury or frost, ("gall-wood") , or even brush- 

 like excrescences of the branches develop, known as "witches- 



1. Lindau^ Bemerk. ub, Bau u. Entwickelung von Aecidium Engler- 

 ianum. P. Henn and Lindau. Engler' s Jahrb. , 1893, Bd.XVII, p. 43. 



2. Compare also loack, Ueb. Schleimranken in d. Wurzelinter- 

 cell. einiger Orchideen. Ber. d. D. Bot. Ges. , 1892, Bd. X, 



p. 645. Hypels. Uotes de Pathologie vegetale. C. R. Soc. Bot. 

 Belgique, 1897, T. XXXVII, p. 246. ("prolongements de la mem- 

 brane cellulaire") . 



