ECCENTRIC GROWTH. 289 



There can be little doubt that the explanation of the Tropaeolum 

 flower is remarkably simple, once the effect of an unequal rate of 

 growth on one side of the whole shoot and its appendages is 

 understood, and that such construction diagrams not only include 

 between them the facts of observation, but point out the degree 

 to which variation may be expected, according to the amount of 

 eccentricity obtaining at the moment of observation. 



The flower of Tropaeolum majus is thus in all probability a 

 (3 + 5) asymmetrical type throughout; its eccentricity being still 

 further complicated by : (1) the delayed development of the 

 corolla, so frequent in petaloid types, these members being greatly 

 retarded at first, so that the relation of the corolla cycle to the 

 spiral sequence is not apparent; (2) the stamens also present a 

 degree of growth retardation which causes them to lose at an 

 early date the normal contact-relations of a (3 + 5) system, and 

 so loosen out until the contact-relations of the next type (5 + 8) 

 are approximated (fig. 99), in which eight members are required to 

 fill a contact-cycle. A ninth stamen, if produced (No. 19). would 

 be median anterior, and the orientation of the carpels slightly 

 oblique. 



As opposed to the Eichlerian type of diagram, a convention 

 based on the visible structure of the bud, these schemes become 

 structural diagrams for the primary distribution of growth-energy 

 in the initiation of the floral members. An attempt has been 

 made in fig. 99 to approximate the amount of eccentricity re- 

 quired to agree with known data, if the system had retained 

 uniform growth in all its parts ; the fact that the fiower illustrated 

 is " left-hand " resulting from the direction in which the funda- 

 mental construction curves cross one another (fig. 34). 



Given these fundamental phyllotaxis phenomena as the basis 

 of the construction of the fiowering axis, it now becomes possible 

 to isolate all superimposed variations and alterations in the 

 relative rates of growth which collectively determine the formation 

 of a floi'al mechanism from a mere collection of uniform lateral 

 appendages. 



