2G8 THE FLOWER. 



it is hypofjTjnoiis (466), when free from all union either with the pis- 

 til or the calyx, as in the Rue and the Orange (Fig. 434). It is 

 perigynous (407), when it adheres to the base of the calyx, as 



in the Buckthorn (F.ig. 435, 

 43G) ; and Avhere the calyx is 

 adnate to the ovary, as in the 

 Apple, Hawthorn (Fig. 390), 

 «S:c., there is commonly a disk in- 

 terposed between the two. The 

 disk is sometimes expanded on 

 the summit of such an ovary, when it is said to be epigynous (469), 

 as in Cornus, and all Umbelliferous plants. 



Sect. V. The Floral Envelopes in PATmcuLAR. 

 490. Their Development, or Organogeny, first requires a brief notice. 



The flower-bud is formed in the same way as the leaf-bud ; and 

 what has been stated as to the formation of the leaves of the branch 

 (273) equally applies to the leaves of the flower. The sepals are 

 necessarily tlie earliest to appear, which they do in the form of so 

 many cellular protuberances, at first distinct, inasmuch as then their 

 tips only are eliminated from the axis. Each one may complete its 

 development separately, like an ordinary leaf, when the sepaLs re- 

 main distinct. Or the lower and later-eliminated portions of the 

 forming organs of the circle coalesce as they grow into a ring, which, 

 further developed in union, forms the cup or tube of the gamophyl- 

 lous calyx. In some cases, it would appear that the sepals may at 

 first grow separately, and afterwards, though only at a very early 

 period, coalesce by the cohesion of their contiguous parts. The sev- 

 eral parts of an irregular calyx are at first equal and similar ; the 

 irregularity appears in their subsequent unequal growth. The pet- 

 als or parts of the corolla originate in the same way, a little later 

 than the sepals. Their coalescence in the gamopetalous corolla is 

 congenital ; the ring which forms its tube appearing nearly as early 

 as do the slight projections which become its lobes and answer to the 

 summits of the component petals. The rudiments of the petals are 

 visible earlier than those of the stamens : but their growth is at first 



FIG. 435. Flower of a Buckthorn, showing a large perigynous disk. 436. Vertical section 

 of the same. 



