156 



falls far telow the forimtion of shoots °''^^''^ 



The development of adventitious shoots from callus 1r n-r 

 rested by the formation of side shoots in the cSttin^s which 

 carry it; on the other hand, a luxuriant formation SI callus 

 often hinders the production of adventitious roots on the cut 

 surface. Sorauer has already referred to this? 



;ive 



^ The Investigation of conditions under which ve^etat^ 

 points are formed in callus and under which shoots, or rather 

 roots, are produced, promises many Interesting results. X ro- 

 +H®L!!f2^^^.*° Sorauer 's statement^ according to which callus 

 tissues of conifers, Ericas and other plants do not produce 

 roots until after artificial incision. 



Wound-wood 



Besides a thin walled, homogeneous callus parenchyma, many 

 plants, after injury, produce tissues of other kinds, which be- 

 come similar to wood tissue through a develpment of tracheal 

 elements. The tissue resembling wood, v/hich is formed after 

 injury, is distinguished from normal xylem by its simple his- 

 tology, r/e will terra it wound -wood and for this reason add it 

 to the list of kataplasms"; ' "^ 



The fact must now be emphasized that tissues of the kind 

 described, resEsrabling wood, are usually produced not onlv af- 

 ter wounding but also by the action of other injuries* in the 

 present chapter, we will speak not only of the wood formed on 

 the wounditself but also of other tisvsue products resembling 

 wood, whatever may be the interference to T/hich they owe their 

 (174) production. Those products will be described in a later sec- 

 tion which arise after infection by foreign organisms, - thnt 

 la "gall -wood". 



We described above the case studied by Kny and other's, in 

 v/hich yoiing shoots split lengthwise can fill out anew the in- 

 terrupted cambium ring in both iialves by means of callus tissue, 



1 Wiesner (loo, cit.) observed as exceptions some Taraxa- 

 cum root cuttings, which had formed sprouts on both sides. It 

 would be interesting to follow the further development of such 

 root pieces and to prove whether posslbljr and in how far the 

 doiible development of shoots infltiences their histology. Fur- 

 ther literature on Taraxacum in lakker, Onderzoekingen over Ad- 

 vent iv© Knoppen. Amsterdam. 1885; Goebel, Ueb. Regeneration in 

 Pflanzenreich. Biol. Cbl., 1902, Bd. XXII, p. 385. 



p 



In the process of rQot formation and bud-development 

 in willows, described by Vochting (loc. cit.) the polar con- 

 trast seems to be independent, to a high degree, of external 

 factors. Its reversal has not yet been possible. The same 

 holds good in my opinion for t]}e polar Bryopsis, with which 

 Winkler worked, (Ueber Polaritat, Regeneration und Heteromor- 

 ' phose bei Bryopsis, Bringsheim's Jahrb. f. wiss. Bot., 1900, 

 Bd. XXXV, p. 449. 



^ Populare Pflanzenphysiol-ogje f. Gartner, 1891, p, 169. 



