CHANGES OF SHAPE OTHERWISE CAUSED. 163 



crenatus, we have an interesting example of a variation essen- 

 tially of the same nature, little as it appears to be so. For 

 each of the lateral indentations is here the seat of an axillary 

 bud ; and these we see are separated by internodes which, 

 becoming broader as they become longer, and narrower as 

 they become shorter, produce changes of form that correspond 

 with changes in the luxuriance of growth. 



To complete the statement it must be added that these 

 variations of nutrition often determine the development or 

 non-development of lateral axes ; and by so doing cause still 

 more marked structural differences. The Fox-glove may be 

 named as a plant which illustrates this truth. 



240. From the morphological differentiations caused by 

 unlikeiiesses of nutrition which the whole plant feels, we pass 

 now to those which are thus caused in some of its parts and 

 not in others. Among such are the contrasts between 

 flowering axes, and the axes that bear leaves only. It has 

 already been shown in 78, that the belief expressed by 

 Wolff in a direct connexion between fructification and innu- 

 trition, is justified inductively by many facts of many kinds. 

 Deductively too, in 79, we saw reason to conclude that such 

 a relation would be established by survival of the fittest ; 

 seeing that it would profit a species for its members to begin 

 sending off migrating germs from the ends of those axes 

 which innutrition prevented from further agamogenetic mul- 

 tiplication. Once more, when considering the nature of the 

 phsenogamic axis, we found support for this belief in the fact 

 that the components of a flower exhibit a reversion to that 

 type from which the phaenogamic type has probably arisen 

 a reversion which the laws of embryology would lead us to 

 look for where innutrition had arrested development. 



Hence, then, we may properly count those deviations of 

 structure which constitute inflorescence, as among the mor- 

 phological differentiations produced by local innutrition. I do 

 not mean that the detailed modifications which the essential 



