31 



— 0.106 and -+- 0.29 ; and for those of Malva imlgaris 



— 0.055, — 0.09 and +0.12. Especially with the first two 

 plants thèse sensibility-coefficients diverge considerably, 

 which proves how very différent the influence of nutrition 

 is on the variability of the différent characters of a plant. 

 By the same change in nutrition the variability of one 

 character is hardly modified at ail and that of another 

 character of the same plant very considerably increased 

 or diminished. 



It is very important to know in what direction the 

 nutrition reacts on the variability, whether under unfa- 

 vourable nutritive conditions the variability is either always 

 greater, or generally smaller or whether the two cases are 

 equally fréquent. In this respect the table shows us that 



for 6 out of 14 characters the sensibility-coefi&cient of ~ 



is positive which means that the variability of the well-fed 

 plants is greater than that of the badly-fed ones, whereas 



in the other characters the sensibility-coefficient of -— is 



négative which means that the variability is greatest in 

 the badly-fed plants. 



Even with the same species one character shows a greater, 

 another a smaller variability when the cultures grown 

 under favourable and unfavourable nutritive conditions are 

 compared. With Iheris amara the length of the plants from 

 the fertile earth is more variable than that of the plants 

 from the sandy soil, other characters, on the other hand, 

 show greater variability in the badly-fed culture. In the 

 same way in Anethum graveolens the variability is greatest 

 with the number of lobes of the well-fed plants and with 

 the number of flowers and umbel-rays of the badly-fed 

 ones, while with Malva vulgaris the length of the leaf-stalk 

 and the number of akènes of the well-fed plants, but, on 

 the other hand, the length of the blade of the plants from 

 the sand, show the greatest variability. 



