526 



phosphoric acid wandering into the young growth, possibly one-fifth comes 

 from the trunk, and four-fiftlis from the root and soil. These figures favor 

 the theory that the root-body, to a still higher degree than the trunk organs, 

 gives up its rcser\ c [)ro\ ision of nitrogen, phosphoric acid and [)otassium. 



Deficient Gkeemng of Younger Leaves. 



A special form of the eft'ect of lower temperatures on the coloring of 

 plant bodies is the remaining yellow of grozving organs due to the lack of 

 temperatures necessary for turning green. Klving' found that ctiolin was 

 formed at temperatures which were still too low for the formation of 

 chlorophyll in spindling seedlings, which, cxi)osc(l for a short time to the 

 light, became yellower than those left in the dark. When plants are uncov- 

 ered in the early spring, numerous examples are found in which the etiolated 

 shoots which had been produced under the cover, in s])ite of the at times 

 abundant illumination, generally do not lose their yellow color or lose it 

 only slowly and irregularly in spots. The most abundant examples were 

 furnished by garden hyacinths. If these are uncovered too early in the 

 spring and frost surprises the young leaf cones which are not yet green the 

 leaves develop later a normal color but their young tips remain white or 

 yellow. 



In the parts which appear yellow, we usually find the chloro])lasts 

 formed and arranged normally, i. e., along the free lying parts of the cell 

 walls or those bordering intercellular passages (epistrophe), but the color 

 ing matter is only a more or less intensive yellow. In this stage, all possible 

 transitions, up to the complete absence of the grains in the wholly bleached 

 tip of the leaf, are found ; these are not, however, conditions due to disso- 

 lution but are arrestment formations. In the whitest parts of the meso- 

 phyll, the cells are filled with a watery cell sap which is traversed by 

 cytoplasmic cords, without the deposition of any chlorophyll bodies in the 

 cytoplasmic wall layer. In other cells of the yellowish parts, the differenti- 

 ation of the contents extends to the primordia of the chloroplasts, but these 

 appear more whitish, more tender, we might say, and at times, cloudier, 

 less dense and less sharply defined. Normally formed, intensively green 

 chloroplasts are finally found in the parts of the leaves which have grown 

 out of the soil after frost action. At times the lack of green is connected 

 with the presence of red coloring matter. Charguerard" furnishes an 

 example ; he obser\ed in Plialaris ariindinocea picta, that the young leaf tii)s, 

 with their well-known white stripes, appeared reddened by frost. The rose 

 red coloring disappeared with warm weather. .Schell'' confirms the appear- 

 ance of the red coloration with cold. In the spring he placed plants with 

 red-colored, young leaves under three different tem])eratures and observed 

 that the specimens kept in a room at 15 degrees C. became green within 



1 Arbeiten d. Bot. Instituts zu Wiirzbuig, Vol. II, I 'art 3; cit. Bot. Centralbl. 

 1880, p. 835. 



•.; Revue horticole, Paris 1874, p. 249. 



3 Botanischer .Jahrcsbericht 1876, p. 717. 



