160 



wood (veined or grained)*". 



It majr be seen from microscopic investigation, thp.t def- 

 inite groupings are regularly repented in the irregiilar course 

 Of the fibres, . In vertical longitudinal sections, especially 

 If the wound V7ood hr.s already attained some size, fibres ap- 

 pear which have been cut slantingly and crosswise, "Just as 

 the elements already produced may vary in length, considerable " 

 disturbance In their normal perpendicular course is found which,, 

 always beginning at the edge of the callus, spreads upward and 

 /,»«% ^^»^^^r^". (Mfiula). Among many Irregularities the frequent 

 (178) ueourrenoe of ?-^ 0-, ot W- IUe© twisted cells Is very notice- 

 able, ThSse are 'united into groups like balls of thredd, 

 (compare flg» 69) as well as context for fig. 102). All ele^. 

 ments bdf wound wood can participate In the construction of 

 these balls. In those pictured la flgur© 69, tal^en ftom the 

 wound wood of Abies oephalonlca . ijarenchj/ma cells as well as 

 tracheids are found, Tracheids always play the chief role, 

 AS M&ula has proved, the wound wood of different plants is 

 characterized by the different sl«e and the different distri- 

 bution of Its ball-formrtlons. Figure TO throws light on the 

 form of the separate cells T/hioh oinpose these balls. It rep- 

 resents a few strikingly twisted tracheids, here and there 

 branched, from the wound wooa of Qydonla japonloa . The middle 

 one of the three contains a spiral band. Besides the slender 

 tracheids, short, barrel-like ones are produced and parenchy- 

 matlo elements often of wonderfully Inflated branched forms. 

 According to vSchtlng (loc, clt, p. 136) similar fotms are 

 found also In the abnormal bark -formed after Injury, which 

 we can term "wound-bark". In this occurs also the formation 

 of balls as In ifjund-wood ( Cydonla .japonica ), 



vSchtlng (loc, dt, p. 152) described this ball-like ar- 

 rangement of the wood-elements In the wound wodd of Cydonia 

 japohlca . which was formed In grafting experiments inwhIcK* 

 the bark rings 7;ere Inserted upside down. These and other ab- 

 normal tissue formations after grafting on Beta vulgaris and 

 other objects led vBchting to the assumption that "the individ- 

 ual elements of the l.ong axis are constructed with a polar re- 

 lation, and that th^lr poles are drawn together or pushed away 

 according to whether we brlgg the unlike or the like into con- 



■^ The formation of gnarls occurs not only after injury, 

 but also in abnormal tissues of other origin. We will have to 

 speak repeatedly of "gnarl tubers" and gnarl structure. Compare 

 also Prank, Krankh, d. Pfl., 2. Aufl., 1895, Bd. I, pp. 80 ff. 

 At this point I would like to call attention casually to the 

 fact that an irregular course of the fibres csn even occur 

 where there is no question Whatever of hyperplastic formation 

 of tissue. Rj, flartig has proved recently, that the "waved or 

 grained slyuotuare" In trees is often to be traced back to the 

 longitudinal pressure, "which a side root, growing much thick- 

 er towards the top, exerts on the ' bajrk and cambium of the lower 

 end of the trunk, or vfh%qh the branch. In becoming thicker, 

 /exerts above and be Jew qn the b^rk of the 'tree, Thi^ longi- 

 tudinal i^tesBl^re causes foldings In the bark of thin barked 

 trees, and in. the wood produced from the cambium. These run' 

 in a longitudinal directions. In trees with thick bark (oak, 

 chestnut, blaekwalder), Qri'accoutt of longitudinal pressure, 

 the elements of, the inner bark and of the wood are wound in 

 wavy-lines^ running tangentially. In conifers, waved wood oc- 

 curs rarely, In tbe trunk". (Holzuntersuch, , Altes und lleuws, 

 1901, p, 5g, Ueber die Ursachen d. Wimmerwunchses (Wellenhpl- 

 zes) der B«ume. Obi, f^ ges, I'oretweaen, 1901, April). 



