19 



Weisse ') investigated the influence of nutrition on 

 varions characters of Helianthns annuus and found that the 

 arithmetical mean for ail the characters studied is smaller 

 with plants cultivated on a sandy soil than with well-fed 

 plants. His numbers, (for each culture about forty) are too 

 small, however, to allow us to calculate the constants for 

 médian and variability from them and to draw conclusions 

 from thèse. 



Mac Leod'') made experiments in order to détermine 

 the influence of nutrition on the number of ray- and disk- 

 flowers of Centaurea Gyanus and found that thls number 

 is the smaller the more the nutitrive conditions are unfa- 

 vourable. Besides he investigated the influence of good 

 and bad nutrition on the number of stigmatic-rays of 

 Papaver Rhoeas coccineum aureum. He arrived at the resuit 

 that with the badly-fed plants the médian is considerably 

 smaller, but that the variability of the character is increased 

 by the bad nutrition. 



From this short summary it will appear that in very few 

 cases only the quantitative change, caused in the médian 

 by varying nutrition, has been determined. It is désirable 

 to extend the number of observations on this point, but 

 it is especially important to learn the influence of nutrition 

 on the variability for several characters and plants. Two 

 questions hère arise, in the first place whether this in- 

 fluence is différent for différent parts of the same plant, 

 in agreement with Versch affelt's 2) resuit that the va- 



1) Arthur Weisse, Die Zahl der Randblùthen an Compo- 

 sitenkopfchen in ihrer Beziehung zur Blattstellung nnd Ernâlirung. 

 Jahrb. f. wiss. Bot. Bd. 30, 1897, p. 453. 



2) J. M a c L e d. On the variability of the disk- and ray-flowers 

 in the corntlower {Centaurea Cyanus). Hand. v. h. 3de Vlaamsch 

 Nat. en Geneesk. Congres, Sept. 1899, p. 61 (in Dutch) and On the 

 variability of the number of stigmatic-rays in Papaver. Hand. v. h. 

 4de Vlaamsch Nat. en Geneesk. Congres, Sept. 1900, p. 11 (in Dutch). 



3) Ed. Verschaffelt, Ueber graduelle Variabilitât von ptlanz- 

 lichen Eigenschaften. Ber. d. d. bot. Gesellsch Bd. XII, 1894, p. 350. 



