58 



plants, Overton calls attention to the fact that lov/ tempera- 

 tures ma^ possibly effect an increased concentration of the sugar 

 contained In the cell. 



In concl-usion, the metaplastic formations of coloring mat- 

 ter In the so-called graft -hybrids must be considered. Linde-" 

 muth , in his grafting experiments with various potato species, 

 grafted above ground the pale green shoot of the "calico" variety 

 with the violet shoot of the "Zebra", After 14 days the grafted 

 axillary paifet below the place of coalescence had reddened active- 

 ly, It is wholly improbable that the reddening of the under part 

 was prodticed by the downward conduction of the pigment; it has 

 not yet been o^&erved, that red pigment can wander from cell to 

 (60) cell. Also nothing '^ known of the esxstence of any ohromogenio 

 or leuco-oonnection, to which this ability to wander could be due. 

 We would dare speak of a gyaft-hybrid, only if it had been made 

 probable that the cells of the stock had been incited^ by the 

 cells of the engrafted scion, to the formation of materiel other- 

 wise foreign to them. In my opinion it is, hov/ever, very much 

 more probable that the injury, perhaps in connection with some 

 factors effective at the time of coalescence, led to the forma- 

 tion of the red pigment^* in the described phenomena on red 

 coloration I can discover no proof of any gra,ft-hybrid nature of 

 the potato plants described. 



Further study of the conditions under which the developmemt 

 of the red pigment ©f the cell sap occurs is greatly desired and 

 promises most interesting disclosures. It is still undecided 

 whether all the phenomena of abnormal red coloration maybe fally 

 explained by the relation to nutrition discovered by Overton. 

 I call attention to Molisch's^ observations, according to which 

 young plants of Barilla nankinensis and Iresine Linden! were 

 colored more strongly in a nutrient solution free from nitrogen, 

 than in cultures in spring water. Overton also made similar ob- 

 servations. 



We may conclude briefly our views in regard to the cell con- 

 tents, which besides the chloroplasts, takes part in metaplastic 

 changes. We have spoken already of the enrichmait of many cells 

 with alb umen and starch under the influence of parasitic fungi 

 or animals. Most remarkable are the accumulations of starch 

 wEiiet Hobba observed repeatedly in his experimental plants ( Poly - 

 gon um fagopyrum ) when unsuitably nourished, Nobbe* saw"a suffo- 

 caTing surplus of starch grains" accumulating in the parenchyma 

 cells of leaves of plants which were insufficiently provided with 

 chlorin. Nutrition with unfavorable potassium salts (saltpeter, 



^ Vegetative Bastarderzeugung durch Irapfung. landwirtsch. 

 Jahrb., 1878, Bd. VII, p. 887. 



^ Compare also the negative results of Laurent, Wouv, rech, 

 s. la greffe de la pomme de terre, C. R. Soc. Roy. Bot. Belgique, 

 1900, T, XXXI2, p. 85. 



^ Blattgrun u. Blumenblau. Schr. Ver. z. Verbreitung natur- 

 wiss. Kenntn, , Wien, 1889-90, Bd, XZX. Further it should fee test- 

 ed whether energetic ventilation of a tissue is also influential 

 in the formation of red coloring matter. Kienhaus (Zur Bildung 

 blauer u. violetter Parbstoffe in Pflanzenteilen, Schweiz, Wochen- 

 schr. f. Chemie u, Pharm., 1895, Kr, 1) states that in the unripe 

 fruit of SolanTjtm nigrum the pigment formation developed first in 

 the places of injury and near the stomata . 



^ Ueber d. physiol. Punktion des Chlors in d. Pfl. Land- 

 wirtsch. Versuchsstat., Bd. VII, 1865, p, 371. 



