78 



The macroscopic symptoms, like the histological con- 

 ditions vary with the degree of the disease. In the case of 

 barks very strongly distended, I fotind that the young peri- 

 derm cells were heing stretched in the same way as those of 

 the bark parenchyma^ and were grov;ing out into sacs, oriented 

 radially. {Compare fig, 19). The cells of the cork-meristem 

 seem to remain unchanged. Here too, after the growth of the 

 cells, there follows the disintegration of the tissue into 

 its single elements* 



•Outgrowths similar to those on cuttings of Ribes aureum 

 arise further, for example, on potato tuvers. At first, 

 when" kept in a moist atmosphere, the above mentioned lenticel 

 ©SiCrescences are formed but then the cells in the neighbor- 

 hcCid. of the lenticels also hypertrophy. The cork covering 

 oracks up in radial rifts and ia places is raised slightly 

 and falls off, producing round v/ounds up to ^ cm, in diameter. 

 in v/hich large-celled^ crystalline, glistening bark tissue 

 is visible^ Finally, these areas of excrescence, proceeding 

 from neighboring lenticels, fuse so that in the end little 

 scales are sloughed off here and there from the potato tuber. 

 The hypertrophied cells resemble essentially those of the Ribes 

 cuttings already described. The normal starch content of the 

 cells of the potato tuber has evidently been used up in the 

 vigorous groT;th» and in any case the hypertrophied cells 

 no' longer contain any starch or only scantjT- remains of it. 



In SambUQUS lajij^s. , the rupture of the bark proceeds from 

 the- lenticeliB ;' here also the young cork cells pais-iicipate in 

 the' hypertrophic growth. Yet I have not seen that such long 

 sacs come from them as in the case of Ribes, Cuttings of 

 Gin^is^o biloba also the lenticels of which seem incapable of 

 forming excrescences (see above), develop bark excrescences. 

 The hyperti'-ophied cells, v/hich I found in the bark of Gingko, 

 were however, not so regularly arranged radially as in Ribes 

 and others, but were oriented irregularly in different di- 

 rections. Bark excrescences appear further in the rose and 

 on the hypocotyl of Phaseolus vulgaris. ^ „ Still further they 



"■*■_,. " _ I n a i ' .Miin ii III 'I ill ■ 'f ill. »i g T,.,_ " 



appear onPxrus malus and Pirus communis , ** and undoubted.ly 



1,. Unfortunately Sorauer makes no detailed anatomical state- 

 ments. Perhaps the changes T/hich he observed are identical 

 v;ith those described by Pferseka (Formverand, d. V/urzel* in 

 Wasser u* Erde, Dissertaion Eeipsig, 1877) . 



Er Gpmpare d. Jahrsber d, Schles Gentravalverins f , Gartner 

 u.. G«,rtenfreunde, Breslau 1881; further Atkinson, Oedema on 

 apple trees. Hep. Agr, Exp* Sta. Ithaca, U. Y. 1893, p. 305; 

 also Sorauer* s Angaben uber Streckung der Rindenzellen (Ueb« 

 Frostschorf an Aepfel- xind Birnenstammen, Zeitechr, f, Pfl* 

 Krankh, 1891, Bd* I, p, 137). A iurther statement of Sorauer' s 

 fUachweis der Verweichlichung der Zweige uns. Obsthaume durch 

 d. Kultur, Ibid, 189E, Bd» II, p, 143). makes it supposable, 

 that the bark cells on the so-called fruit-wood of the pear 

 tree are more delicate and mair be brought more easily to the 

 formation of hyperhydric excrescences experimentally than the 

 bark of other branches of the same species* 



