External Conditions and Manuring. 315 



site leaves to stems with trimeroiis whorls (Fig. 58 /; 

 and a)- 



The arrow A in I^ig. 58 iiidicates the result of im- 

 proved conditions, the arrow B that of more unfavoraljle 

 ones. 



The figure therefore not only illustrates a particular 

 case Imt is a graphic representation of our thesis that 

 high nutrition favors the production of the anomaly. 



This scheme can be applied to a long series of cases, 

 both of anomalies that occur in the field and of highly 

 variable horticultural varieties. The best known example 

 is furnished by the tricolored pansy Viola tricolor ma- 

 xima. Here, as every gardener knows, the spring and 

 early summer flowers have larger, much broader and 

 more intensely colored petals than those of late summer.-^ 

 The greater drought and the gradual exhaustion of ma- 

 nure around the plants are the causes. The same general- 

 ization applies to numerous cases to some of which we 

 will refer in the following section. 



§ 27. THE INFLUENCE OF EXTERNAL CONDITIONS AND 



OF MANURING. 



J. CosTANTiN has dealt with the relation between the 

 plant and its environment in a book devoted to this ques- 

 tion.- In it he treats of the influence of the environment 

 both on the normal characters of the plant and also on 

 varieties and anomalies. An immense range of facts and 

 observations is thus made accessible to the student. 



^V. B. WiTTROCK, Viola-Studier, Acta Horti Bergiani, Vol. II, 

 1897, Nos. I and 2. See also Verlot, loc. cit., pp. 46-47. 



"J. CosTANTiN, Les vcgctaux ct Ics milieux cosniiqucs. Bibl. 

 scientif. Internationale, 1898. The earlier writings of tiiis author 

 have been dealt with in our first volume (p. 99). 



