134 



(147) necessary for the shoot was conveyed, contained abundant ducts 

 an J libriform "fibre© and thick -walled, pitted wood parenchyma 

 xjells. A comparison v;ith equally old "normal" root tubers de- 

 monstrates that In this present case "continued" demand can not 

 have incited the abnormal formajjion of tissue. In the abnor- 

 mally developed dahlias which Voohting described there clearly 

 exists 'an effect of "increasea" demand upon the tissues - an 

 aotivity-hyperplaeia, 



Sirailmz' complications, making more difficult an under- 

 Standing of the iffectire factors, may be found In many galls. 

 If these are produced on petioles, the vascular tissue below 

 them in the Ktem is often inoreased» In our native oaks var- 

 ious cynipides, most frequently Spathe^aster baccarum . cause 

 large, round galls on the'staminate inflorescences. The axes 

 bearing the galls not only live longer than normal ones, but 

 are also distingjiished by a secondary coalescence of their vas- 

 cular tissue. The ass\imption that the increased mechanical de- 

 mand and increased supply of materials and water have given 

 rise to the described changes In tissue, Is especially clear 

 here; nevertheless, the possibility exists that the same secon- 

 dary tissues would be found also if, in some other way and with- 

 out a simultaneous increased functioning of the tissues con- 

 cerned, it were possible to lengthen the life period of the 

 inflorescence axes. 



The histological structure of the abnormal tissues ;)ust 

 described^ reminds us that no sharp boundary may be drawn be- 

 tween homooplasias and heteroplasias. Holding more strictly to 

 the proposed principle of division we would have had to d^etur 

 many a hyperplasia discussed in this section to the next one. 

 As mentioned already the red wood, for example, does not con- 

 sist of entirely normal elements since its cells are somewhat 

 shorter than normal ones, jfn the vascular bundles developed In 

 abnfrmal abundance, which Vochting studied, tracheids of short 

 cylindrical or bgrrel-like form occur, the libriform fibres are 

 rather short etc. The abnormal coalescence of the tissues Is 

 therefore composed of elements vsii ich remain bielow the normal in 

 their size development. They shOTr the same variations from the 

 normal cell structure that we shall find later coming Into ef- 

 fect more strikingly In "kataplasmas". 



t 



On the other hand, Vochting proved that In the abnormally 

 developed vascular bundles of Qxalis crassicaulis , elements 

 may be found in this tissue concrescence which are foreign to 

 the normal tuber. Besides wood parenchjmia cell^, libriform 

 fibres are also produced. In this case therefore the abnormal 

 tissue displays a more abundant differentiation than does the 

 corresponding noiraal one. We will find many differences of a 

 similar kind in prosoplasmas. 



If, in spite of the described structural differences, I 

 have included all under homooplasias, it was because the exist- 

 ing differences seemed too slight for me on their account to 

 have wished to disorganize a group, well characterized physi- 



(148) olcgicaliy. We find, however, often in a normal development of 

 the vascular bundles, tracheal elements develop first of all, 

 and then, by continued growth, wood fibres and wood parenchyma 

 cells. 



2, We spe^ of correlation-h omo oplasias when, as a result of 

 locally effective arrestment in growth, its lofjalized further- 

 ance takes place elsewhere, which leads to homooplastic changes 



