THE FLOWEB. 101 



P. Moutan enclosing them all but tlie stigmas : the apparently inferior 

 position of the ovary of Victoria depends ou the discoid development of 

 the receptacle where the outer floral circles are inserted. A ring of 

 similar nature, free from the ovary, occurs in Alchemilla. Another con- 

 dition exists in the Mignonette (Reseda), where the cup-like or annular 

 development of the receptacle is inside the floral envelopes, and forms a 

 support to the stamens surrounding the ovary. This form of the " disk," 

 which occurs also in Acer (fig. 175), must not be confounded with those 

 depending on the presence of perfect or imperfect whorls of abortive 

 floral organs. The epigynous disk of Umbelliferse (fig. 170) and allied 

 orders is probably a development of the receptacle, since the so-called 

 adherent tube of the calyx is perhaps an excavated receptacle. In 

 Circcea, and to a greater or less extent in other Onagracese, the epigynous 

 process supporting the floral envelopes and stamens is prolonged into a 

 tube above the inferior ovary, surrounding the long free style. Where 

 organs are multiplied, we often find the thalamus lengthened into a 

 conical or clavate body, to give room for the insertion, as with the pistils 

 of Ranunculus (fig. 168), Magnolia, Fragaria, &c. In Geraniacese the 

 receptacle is prolonged into a column in the centre of the confluent styles ; 

 and the same occurs to less extent in Euphorbia. 



When a circle of organs is removed from its predecessor by a 

 stalk-like internode, it is called stipitate. The column supporting 

 the carpels of Geranium (p. 143, fig. 276), or those of Umbelliferse, is 

 termed a carpophore ; the stalk of the ovary of Gentiana is a yyno- 

 phore ; a stalk above the corolla, supporting both stamens and pistils, 

 as in Passion-flowers, is &gynandrophore. The form of the flower is 

 dependent in many cases on the obliquity of the receptacle, as in Le- 

 guminosae, Aconitum, Delphinium, and many other irregular flowers. 



Enation, Substitution, Superposition. The modifications arising 

 from enation have been already alluded to ; while those dependent 

 on the substitution of one organ for another, as in many double 

 flowers where the stamens are replaced by petals, demand only pas- 

 sing notice. Superposition arises from various causes, as from the 

 abortion or suppression of a part that should come between and 

 alternate with the superposed parts, or it may arise from chorisis 

 or enation, or from true superposition of successive cycles, as in 

 tSabia, and possibly by growth in the axil in the same way that a 

 bud is axillary to a leaf. 



Causes producing modifications, The modifications met with in the 

 construction of flowers may be dependent upon arrest, exaltation, or per- 

 version of growth or of development, either separately or in conjunction. 

 By growth is meant mere increase in bulk, by development the progressive 

 change in the form and structure of organs (metamorphosis) which takes 

 place in the course of their passage from the initial to the adult stage. By 

 the action of the causes above mentioned, the parts of a plant vary in com- 

 position (simple or divided leaves, &c.), number (increased or diminished), 



