THE BILATEKALITY OF APPENDAGES. 297 



members is thus associated with a certain amount of sliding- 

 growth, it does not follow that the two phenomena are in any way 

 dependent one on the other; the progressive flattening may be 

 clearly ascribed to a reduction in the rate of radial growth, which 

 is common to symmetrical as well as asymmetrical constructions, 

 and must obtain in the transverse component of all dome-shaped 

 apices; the sliding effect may be entirely isolated from such a 

 retardation effect, just as in the diagram the reduction in the rate 

 of radial growth-expansion can be imitated by using a curve 

 expressing this factor, but the sliding effect has to be put in 

 subsequently. 



It becomes apparent that the consideration of the phenomena 

 thus included under the general term " sliding-growth," in con- 

 nection with lateral appendages, requires very careful handling, 

 in that it might evidently be the result of several distinct growth- 

 factors ; and as in other cases, the first-suggested interpretations 

 may not be the right ones. In fact, the true interpretation of such 

 lateral slipping is of great importance, since it constitutes the 

 most important evidence in connection with Schwendener's dis- 

 placement theory : the Dachstuhl theory assumed that flattening 

 implied a pressure, and that such readjustment of the angles of 

 the primordia indicated a displacevient of the whole member, and 

 thus affected the divergence-angle and thereby altered the postu- 

 lated Schimper-Braun construction. The diagrams (figs. 100, 110) 

 sufficiently indicate that no amount of such sliding-growth really 

 affects the primary construction system which is taken from the 

 initial points, i.e. the centres of construction, while, as has been 

 already repeatedly stated, mere fiattening is only the expression 

 of reduced radial growth. 



In considering the meaning of these phenomena it may be 

 pointed out, to begin with, that the displacement of the points of 

 contact of four boundary planes does not necessarily involve any 

 displacement of the original centres of construction ; this, in fact, 

 is the usual result of the effect of lateral contact-pressures, com- 

 parable with the special case of fitting previously indicated as 

 giving to an otherwise orthogonal construction the appearance of 

 hexagonal facetting (fig. 95, Pine-cone), or the typical adjustment 



