5 



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Of many Saxifrages and Crassulaceae etc., if placed in a sugar 

 solution, color an intense red after a few days. 



The red coloration appears very abundantly after injury - 

 The edges of wounds on mutilated stems and injured leaves are 

 often colored very intensely. First of all it remains uncertain, 

 whether contact with the air, distaj:banoe in the conducting paths 

 and the consequences of these or some other factor brings about 

 the reddening. The experiments which I made on leaves of Saxl- 

 f raga ligulatar are interesting. The fully grown leaves of^ETe 

 plant, under such life conditions as are offered in conservator- 

 ies, are q succulent, green, but free from red pigment. Only the 

 younger leaves of the experimental plants were slightly reddened 

 on the edge, as also on the underside of the larger veins. -If a 

 fully grown leaf was out through the mid rib, a red coloration of 

 the wound took place after a few days,- at times only after one 

 or two weeks; but only the side of the wound tovmrd the tip of the 

 leaf became colored, v;hile the opposite side remained u^pigmented. 

 It is evident that the same conditions, as regards the change of 

 oxygen supply etc., exist on both edges of the wound, In order 

 I to explain the one-sided formation of pigment, I would ^ike to re- 

 turn to the old assumption of the decreased sap flow which causes 

 an accumulation of the food stuffs above the place of Injury. 

 The formation of red coloring matter may perhaps be explained as 

 the result of superabundant nutrition of certain cells, just as 

 in Overton's experiments. I would also like to propose the same 

 explanation for the red coloration of wounds in other plants. As 

 in Saxifraga ligulata . the accumulation of food stuffs is pro- 

 duc^d by destruction of the conducting paths and the accu^jiulation 

 of the contents, or, in its turn, represents the result of es- 

 pecial stimuli, produced after the injury. In Saxifraga ligulata , 

 moreover, only the tissue on the veins themselves becomes red, 

 most intensely so, immediately at the place of injury, but clearly 

 recognizable even at a distance of 1 to 1-1/2 cm. from the wound . 



The formation of pigment which takes place through the ac- 

 tion of many parasitic organisms;- mostly to be sure in connec- 

 tion with cell growth and division, may possibly have a similar 

 explanation. Since it is now known that even in those places a 

 strong assimilation of proteids and starch often takes place, the 

 possibility may be considered that here also the formation of pig- 

 ment is caused by the supplying of food substances. Local redden- 

 ing and early ripening under the influence of parasites was des- 

 cribed recently by Kochs^. In the latter instance, the formation 

 of pigment under the influence of light may also be traceable to 

 nutritive factors. 



Overton goes still further in his attempt to explain uni- 

 formly the phenomenon of pigment -format ion. As is well known, 

 a lowering of the temperature accelerates the reddening sf many 



■^ The same independence of the red coloration on the surplus 

 of foodstuffs, necessarily produced by destruction of the conduct- 

 ing paths, may be recognized in wounded or notched branches, whose 

 leases, according to Linsbauer (Einige Bemerk, uber Anthokyanbil- 

 dung, Oest. botan. Zeitschr., 1901, Bd. LI, p, 1, therein also ref- 

 erences to the oldeir literature), turn red above the place of in- 

 jury, below it, however, remaining normally green. This distinc- 

 tion may be explained just as the one observed on Saxifrage leaves. 

 Linsbauer explains the reddening ver^ generally by the distrubances 

 in the transference of material and explains in this way also 

 T)verton's results, "Production and transference of material stand 

 in an entirely unusual misproportion to one another (Linsbauer)". 

 The dissimilarity in the proportion of neighboring parts of branch- 

 es and pieces of leaves above and below the normal spot is natur- 

 ally not explained by this. 



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