240 



evei ?i^L^''S?Lr''*'^n? r^?*^"^^^ ^y the supplying of which 

 ilthe fa?L '' "" condition ta produce chlorophyll 



atio/i7qniJ!S!''''n *° ^^Pl'^i» the metaplastic anthocyanln fom^ 

 ^ni^^-,^?- i "^^^^^ ^^^''^^ ^^^^ ^^°^® P- 58)^ the production of 

 ?n^^oi?n °^;^°''°^°^^'^f^''\^"^ heteroplasias^- and in part also the 

 formation of many callus tissues not by an abnormal new produc-- 

 o,^So+ n^^tritive substances but fey an abncrmal asslmxilation of 

 substances already present and those produced ;hi the normal 

 course of life -processes. Local accumulation of nutritjve sub- 

 stances as a result of abnormally increased transpiration might 

 also be operative in the formation of wound-cork. 



No absolutely certain example has been known as vet in 

 which abnormally increased suppljrlng of nutritive substances 

 from without can promote the formation of tissue bejrond the nor- 

 mal amount « Arrestment phrnomena seem rathSfr to bte" caused by 

 abnormally increased transpiration which accelerates the trans- 

 piratory current, as is shown by dwarf examples in dry habitats. 

 -4.^? V ^^^ rate, no normal formation of tissue has been in- • 

 cited by an artificial supplying of organic nutrition from witHu- 

 out - yet it is to be hoped thgt the experiments recently made 

 by Haberlandt and Winkler on isolated plant cells will lead in 

 the future to positive result s. 



Toxic effect s, consisting of degeneration changes of the 

 cell, may be left unconsidered. Those cases are importarrt l«r us, 

 in which an arrestment or a promotion of certain processes is 

 notioegble after the action of any poison. 



Arrestment may be brought about by very different kinds of 

 substances. Some, taken up by the plants in small doses as food 

 stuff and there worked over, can act' as "poisons" v/hen used in 

 greater amounts. Mention must be iriaie here also of the arresting 

 effect of organic food j.n green flagellates, diatoms and others., 

 . vniich become '-apoehlorotio' under the influence of an abnorffally 

 (281) abundant supplying of nutritive su"b£Sar.6&s, Farmer and Ohandler 

 (see above p^ 48) Lave made reports on the arresting influence 

 of air which abounds iii carbon dioxid. In order to arrest the 



^-The formation of correlation-homoeoplasias and heteropas- 

 ias belongs among those cases of abnormal tissue production, in 

 which the abnormal supply of material does not act releasingly 

 perhaps, ^but only as a preparation or as a qualifying effect. 

 If any cambium or anj?' parenchyma capable of division, under the 

 Influence of the supply of food stuff, continues longer the pro- 

 diictlon of cells and acts more intensively than under normal con- 

 ditions, the releasing agent may well be sought in "internal" 

 factors* Similar but more complicated examples are dis.cussed witfe 

 the same point of view by Driesch (Die organischen Regulationen, 

 Leipzig, 1901, p. 118). " I share completely his interpretation 

 «f this matter. It is difficult to answsr the question, as to 

 what factors in hyperplastic formation of vascular bundles in 

 dahlia tubers (Vochting's experiment a) act releasingly as a re- 

 sult of increased demand upon them {Activity- hyperplasia, see 

 above p, 145), whether, ' perhaps in this ©ase, the intensity of 

 the current, i. e. something mechanical, caused the stimulus 

 (Driesc:i loc. cit.) or whether here also only "internal" factors 

 were at v ork and the intensive ciirrent of food stuff created only 

 the necessary nutritive condition, the desired ability to react. 



