32 



the presence of iron and of certain organic food materials. 

 Hence i"^ follows that under differently combined, abnormal 

 life conditions, the formation of the green coloring matter 

 may be suppressed. It is knovm that, in the spring, without 

 experimensbal interference, temperature can influence bulbous 

 growths, grain seedlings, etc., and that these at a low 

 temperature develop yellowish leaves,^ The minimum temper- 

 ature for chlorophyll formation in the "variegated" cabbage 

 variety, B rassica oleracea acephala . studied by Molisch^ is 

 anioh higher than in the above case, In cold fasames, at a 

 temperature of 4 to 7 degrees C, in winter, the plants de- 

 veloped green and white dappled leaves, or leaves completely 

 free from chlorophyll, v/hich, hovv'ever, became green later 

 if the plants were brought into a temperature of from IS to 

 15 degrees C. The leaves newiy formed in the warm chamber 

 v/ere always perfectly green. The fact that, under the cul- 

 ture in the cold frame, the leaf tissue nei^r the veins re- 

 mained predominantly free from chlorophyll, \Thile the other 

 parts of the lamina developed the coloring matter in a norml 

 manner, is worth consideration.'* 



The influence of nutrition may not be ascertained so 

 easily by experiment, since the chemical compounds import- 

 ant for the formation of chlorophyll are produced by the 

 activity of the cells themselves. But the observations 

 should indeed be considered here, regarding the close con- 

 nection which, appears. to exist between the leaf variegation 

 of "variegated" plants, and the place in which they grow. 

 According to Ernst^, a variegated specimen of Solanum ali- 

 gerum . transplanted into garden soil, became monochromatic. 



1, On the necessity of the latter, compare Palladin. 

 ErgrUnen and V/achstum der etiolerton Blatter. Ber, der 

 Deutsch, hot. Gee,, 1891, Bd. IX, p. 4E9. 



2. Compare Sachs, Ueber den Einfluss der Temperatur auf 

 das Ergrunen der Blatter, Flora, 1864, Bd, XLVII, p. 497. 

 Wiesner, Entstehung des Chlorophylls, 1877, to. 95. Rxtzame 

 Bos, Ergrunungsmangel infolge zu niederer Fruhlingstemper- 

 atur. Xeitschr, f. Pflanzenkrankh. , 1892, Bd. II, p. 136. 



•3, Ueb, die Panachure des Kohles. Ber d. D. bot. Ses. 

 1901, Bd, XIX, p. 32. 



4, Timpe floe, cit . p. 7) reports on a specimen o± 

 Ulmus scabra var. viminalis in ths Botanical Garden in Got- 

 tingen, whose spring shoots bore leaves speckled with yel- 

 low, which retained their variation until autumn, while the 

 mid-summer shoots developed pure green leaves. It may be 

 possible that here also an effect of the lower spring tem- 

 perature is present. Also, as is well known, m bulbous 

 growths, forced in spring, the pale color remains constant 

 in spite of a subsequent increase of temperature. 



5, Botan* Miscellaneen. Bot. Zeitg. , 1876, Bd. 

 XXXIV, p. 33,; 



