136 



of tissue, Boirivant»s experiments on defoliated shoots are 

 very instructive, ime asfiimilatory tissues of the bark tyere 

 increaefed "correlativoly" in the shoots. Recently K, Braun^ 

 has made similar experiments qnd proved in Ac on i turn Stoei*kianum . 

 Syr inga vulvar ifl . Cor ylua avellana vt.r, atropurpurea / RosA 

 oentlf olla and others, an Inorerae of ass imlic tor y t i ssue ,' the 

 ntmjDer of layers of which at timee was doubled. In Lciroitua 

 orvalft a nd other?? there was a striking Increase of chlorophyll 

 grains^, 



3« The abnormal tissues occurring on injured plant organs 

 are usually of an heteroplastic oharrcter. I know of only one 

 ^^^ ^^ otillua homooplasia , Schllberszy* succeeded in stiawla* 

 ting an increase of the vascular tissue in stalks of Phaaeolug 

 multlflorus through injury, This occurx-ed betause "the cell i 

 groups, lying close to the phloem bundles, therefore, those a4* 

 Jaoent to the innermost layers of the parenohytaatic primary 

 bark, became adjusted for division, after some p/eoedins Injury, 

 (by an interruption of tho vascular bundle cylinders, closing 

 upon one r.nother like rings), Thus they took the form of seoon- 

 lXA9) dary meristem." The newly produced m^?ristematic zone acts like 

 the oarabial, producing xyXem rnd phloem, Figure 59 shows part 

 of a orose-section through a phaseolns stalk. Outside th© bar<l 

 bftat bundle are visible the newly produced xylem «.nd phloem* 



We arrcnged the material of our last three sections from an 

 etiologloaX point of view, but in them surely have not named all 

 the factors, by which horaooplastlo formations of tissue ean b e 

 included in any one of the three previously named groups, the 

 products of which, ef I suppose, might have shown an homooplastle 

 character. In places on the laterally comp-ressed internodes, the 

 calls of the permanent tissue 7- ere incited by the force of com- 

 pression to a growth perpendictJlar to the direction of the pres- 

 sure and also to repeated cell division, 



Kny observed similar abnormal division under similar condi* 

 tions, in the pith of Bryophyllum oalyclnum and Begonia*. 



I know of „no positive case ':7here, by the action of foreign 

 organisms, homooplastle exoreecenoes of tissue - "gall-homoo- 

 plasios" -. would have been produced. In all galls produced by 

 abnormal cell division, ve are concerned with heteroplastic tis- 

 suefli, differing from the corresponding normal tissues in the 

 nature of the differentiation and the volume of the separate 

 elemonte,-. nrhen the fundamental tissues are simpler histologi- 

 cally, this may often be the only difference. 



^ Boirivant, Reoh* s, l» trganes de remplacement cheat: I. 

 pi. Ann. So. Hat. Bot., 1897, VIIl, Ser,, T. VX, p. 307. 



^ Ueber Verand, im Gewebe entlaubter Stengl u, Zweige. 

 Dissertation Erlangen, IS99. 



^ One may conclude upon n correlation-effect in the abuntr 

 dant formation of trichomes en the inflorescence stalks of Rhus 

 Cotinua, whose bloom ha* not been fertilised. Indeed this for« 

 ^tion of tldsue should not be designated as "abnormal'*, 



* Kunstllch hervorgerufene Bildung sekundKrer (extrafasci- 

 cularer) Gefassbundel bei Dikotylodonen, Ber, d. D. Bot, Ges, 

 1892, Bd. X, ^ 424. 



^ U^b, d, Einfl, V, 2ug, u, Druok auf d, Rlchtung d, 

 Scheidewande in sioh teilenden Pflanzenzellon, Pringsheira's 

 Jahrb* fur wiss, Bot* 1901, Bd. XXXVII, p. 55, 



