24 



dotted one, both having the same absciss. Of both the 

 observations hâve been combinée! to groups with the same 

 interval. In ail the figures the size or the number of the 

 part in question increases from left to right. 



Thèse curves now show us the way in which the studied 

 characters vary and the limits of this variation. 



Looking at the various figures we notice that the studied 

 characters generally give fairly symmetrical curves, dis- 

 regarding smaller irregularities. Only in a few cases, as 

 with Anethum graveolens for the number of umbel-rays 

 of plants on the sandy soil, flg. VI, for the number of 

 lobes of the leaves of the well-fed plants, flg. VIII, and 

 besides for the number of lobes of the leaves of Scandix 

 Pecten-Veneris of the fertile soil, fig. IX, the curve is 

 markedly oblique. Only for the number of branches of the 

 third order of Iberis amara from the sandy soil, fig. V, 

 a semi-curve has been obtained. 



Examining in the various figures the position of the two 

 curves with respect to each other, it appears that they 

 partly coincide. This means that in the two corresponding 

 cultures plants are found in which the organ under 

 considération is as large or occurs in equal number in 

 the well-fed and in the badly-fed plants. But at the same 

 time they show that in one culture individuals occur, in 

 which a deflnite part is so strongly or feebly developed, 

 as are not to be found in the other culture. The figures 

 further show that in ail cases except of the number of 

 akènes of Malva vulgaris, fig. XIII, the curve of the plants 

 on sandy soi! has been shifted to the left wùth respect to 

 that of the well-fed plants. 



The observations now enable us to détermine how great 

 the influence of the nutritive conditions is in the various 

 cases and whether this différence in development between 

 the two cultures is the same for various parts of the 

 same plant. 



