841 



preoess of cell-division, (Jarasf?iraoff used substances v;hich 

 act as "poisons" in every concentration and under all oiroum- . 

 stances. It is poB^^ible to produce successfully asporogenic 

 "races" in different kinds of bacteria, by treatmeni 'vith var- 

 ious aoi*s (hydrochloric, rosol and orrbolic acids)"''. 



The exciting effects of poisons becomes noticeable there- 

 fore vrhen it is posaible to increase the gro rth intensity of 

 lOT/er or higher plants by treatment %7lth anaesthetics or metal- 

 lic compounds, Abnormal tissue formation as a result of the 

 exciting action of toxic substances has been repeatedly des^ 

 oribed above. Poisons produced by necrotic decomposition of 

 the cells and tissues seem able, under certain conditions, to 

 incite the formation of 'ound-cork and wound -wood« As T7inkl6r 

 has shown (see above p. 98) forelg'ti substances, supplied from 

 without, are able to incite cell-division. Finally the action 

 of poisons Is also the cause of gall formations,- such as, for 

 instance, all prosoplasmaa, 



S, Turgor ,1 Osmotic gressure and 3)1 ffus ion- Current a 



The significance of water in the processes of cell g rov^th 

 and tissue formPtlon lies ©specially In the fact that all these 

 processes are iptJislble ©nly when a definite amount M water is 

 present. The "preparatory" action, proceeding frem a supplying 

 of v/ater and its absorption, is unmistakable. Only wltli a ^J*'. 

 Inite degree of turgor do the cells become capable of an activity 

 which leads to a normal or to an abnormal [formation of tissue. 

 The question as to v/}® ther increase or decrease of turgor can 

 set free definite formative processes still remains to be dis- 

 cussed. 



In feet, examples are known for an action of this kind due 

 to changes in turgor. I include here especijilly hyperhydrio 

 tissues (compare p, T4). When the amount of water given off jy 

 any cell whatever is reduced, the turgor of the cell will be in- 

 creased by a continued absorption of water. By this abnormally 

 high turgor, the cell is incited to growth -activity, producing 

 long cylindrical tubes, such as those pictured in figures 19. 

 23 and others. The abnormal amount of water mak©s possible the 

 stimulus to which the cell reacts v/ith growth « 



We have named first of all ca^es in which, by the absorp- 

 tion of water, (the increase of turgor) the cells have been in- 

 cited to definite action. The question must still be settled, 

 as to whether formative stimuli can also proceed from changes 

 of an opposite kind. 



Pree-lying cells, like fungus hyphae, root hairs, unicellu- 

 lar forms and the like, are easily accessible for experimenta- 

 tion. Root-hairs are especially useful since they react very 

 easily and ouickly to influences of all kinds. Wie^Jefo'^^S^i^?? 

 described above (p. 120) and easily produced Pjove that abnormal 

 processes of growth and set freeeven in a treatment with^materiai^K 



^'compare"f or 'example Behrlng, Asporog, Milzbrand, ^eitschr. 

 f. Hyg., 1889, Bd, VII. 



^ The Interpretation of the authors who spegk of the growth 

 as a direct result of turgor ("a« a force effect") is erroneous. 



