446 BOTANICAL GAZETTE [may 



older work, that there is also a specific formative action of the blue rays as yet 

 unexplainable on the nutrient basis. 



He has often distinguished between the amount of carbon synthate and the 

 amount of salt nutrients as formative factors in the plant, especially in con- 

 nection with reproduction; and now Fischer^ makes this more definite by 

 considering the nitrogen supply as the most important formative factor 

 furnished by the salts, and by speaking of the carbon nitrogen ratio (C/N) of 

 plants. He probably would not deny that the supply of other nutrient ele- 

 ments, phosphorus, calcium, potassium, etc., have at least minor formative 

 effects and often of an opposite nature from nitrogen. This ratio can be 

 increased by increasing the photosynthesis of the plants or by decreasing the 

 nitrogen supply. The ratio can be decreased by decreasing photosynthesis or 

 by increasing the nitrogen supply. Fischer comes to this important conclu- 

 sion. Very high C/N in plants favors flowering, while a low C/N favors veg- 

 etation. His conclusions are largely based on his own work on the effect of 

 increased partial pressure of carbon dioxide upon the development of plants, 

 but not upon chemical analysis of the tissues. 



Kraus and Kraybill^ have recently worked upon the tomato, varying 

 the C/N in it by varying its nitrogen supply. On the basis of extensive cultures 

 and chemical, microchemical, and anatomical studies, they come to the follow- 

 ing conclusions: (i) a very high C/N gives little vegetative growth and poor 

 reproduction with a high percentage of dry matter; (2) medium C/N gives 

 moderate vegetation growth, good reproduction, and a medium percentage 

 of dry matter; (3) very low C/N gives ver>^ vigorous vegetative growth, 

 little reproduction, and a low percentage of dry matter. Kraus's extensive 

 horticultural investigations enable him to give much evidence that the C/N 

 ratio is a factor of great significance in determining fruitfulness in many 

 economic plants. The contribution apparently puts into the hands of pro- 

 ducers one of the important means of controlling fruitfulness. Fischer's 

 less extensive and one-sided attack caused him to miss the fact that a very 

 high C/N not only reduces vegetative growth but diminishes reproduction. 



These papers have thrown much light on some of the nutrient factors 

 modifying vegetation and reproduction in plants. — Wm. Crocker. 



Loss of chlorophyll. — Meyer'' notes that in Tropaeoliim majus, growing in 

 pots in a greenhouse, the young leaves at the top of the stem are dark green, 

 while the progressively older ones down the stem are green, bright green, yellow 



2 Fischer, H., Zur Frage der Kohlensaure-Einahrung der Pflanzen. Garten- 

 flora 65:232-237. 1916. 



3 Kraus, E. J., and Kraybill H. R., Vegetation and reproduction with special 

 reference to the tomato. Oreg. Agric. Exper. Sta. Bull. 149. pp. 90. 1918. 



-I Mey-er, Arthur, Eiweiszstoffwechsel und Vergilben der Laubblatter von 

 Tropaeoliim majus. Festschrift zum Ernst Stahx. pp. 85-127. Jena. 1918. 



