THE FLOWER AND FRUIT 



91 



of two factors, the differential growth rate of the cycles of floral 

 primordia, and zonal or partial conjoint growth of the outer cycles. 



(Fig- 33-) 



In epigyny, differential and zonal growth occur to a greater 



degree and the apical growth of the morphological end of the 



floral axis is inhibited. The zonal growth of the outer cycles forms 



Fig. 31. Ranunculus ; development of the hypogynous flower. A, the floral axis with 

 terminal primordium and two lateral floral axes; B-D, progressive stages in the ontogeny of 

 the flower; £, four stages in the development of a carpel and the single ovule. 



an enclosing structure which is non-diverged from the walls of the 

 ovary. The styles, stamens, petals, and sepals are then diverged 

 as separate structures from the top of this common zone of tissue; 

 or there may be further expression of non-divergence, a common 

 case being that in which the corolla is a tubular structure of non- 

 diverged petals. Many intermediate stages between hypogyny and 

 complete epigyny occur in floral development, and this again 

 points to the fact that differences in floral type are more of a quan- 

 titative nature than qualitative. (Fig. 34.) 



