THE FLOWER. 97 



found in the monopetalous Orders, where we seldom have more than 

 two. 



Suppression of organs becomes exceedingly striking when associated 

 with suppression of entire whorls. Thus in Callitriche the floral enve- 

 lopes are wanting, and while the pistil indicates the tetramerous type, 

 three stamens are suppressed, so that the perfect flowers consist of one 

 stamen and one pistil, and the imperfect flowers often met with are com- 

 posed respectively of a stamen and a pistil. The latter condition occurs 

 also in the greatly reduced flowers of our native species of Euphorbia^ in 

 which the involucre encloses one naked female flower, consisting simply 

 of a pistil, and a number of naked male flowers reduced to the condition 

 of a single stamen (see Euphorbiaceee). 



A curious kind of regular suppression, not interfering with symmetry, 

 is sometimes met with, where the typical pentamerous condition is re- 

 placed by the tetramerous, either in floVers of the same plant or on different 

 individuals of the same species. Thus, in JRuta, in some species of Sedum, 

 and some Alsinece, the flowers have the organs sometimes in circles of 

 fives and sometimes in circles of fours, without any other accompanying 

 deviations from the character of the species. 



Congenital Union or Inseparation. Union of the organs of the 

 flower consists either in cohesion of the parts of 'a whorl with their 

 fellows, or in adhesion of organs of one whorl to those of another. 

 Both occur in almost every possible degree. It must be borne in 

 mind, however, that these terms are often applied to cases wherein 

 there has really been no union of previously disunited organs, but 

 a want of separation between parts originally uniform, but which 

 in other cases become in process of growth disjoined. 



Cohesion occurs in the calyx, producing what is called a gamosepalous 

 or synsepalous calyx ; also in the corolla rather less frequently, forming 

 a ffamopetalom or sympetalous corolla. With these terms are contrasted 

 polysepalous and polypetalous (or dialy-sep-petalous), used to indicate that 

 the sepals and petals are distinct, i.e. not coherent. 



In the Vine the petals cohere above, while they are distinct below, 

 and the flower opens bv the separation of the corolla from the receptacle ; 

 the sepals of Eschscholtzia are entirely coherent, and fall oft' like a cap. 



Union is less common among the stamens ; but in some Orders they 

 are coherent by their filaments into one piece (nionadelphoiis), in others 

 into two or more parcels (diadelphous). Such cases are usually due to a 

 branching or lobing of the primary staminal leaves, and not to any real 

 union of previously disconnected parts. Other plants have the anthers 

 coherent (syngenesious) , while the filaments are free ; and in some diclinous 

 flowers the stamens are united into a kind of column. 



The carpels exhibit every degree of confluence, from a slight coherence 

 at the base to a firm union by their sides, complete confluence of the 

 ovary with the styles free, confluence of ovaries and styles in part or 

 entirely with free stigmas, and complete confluence of ovaries, styles, and 

 stigmas. In Asclepiidaceas we have confluence of the styles, while the 

 ovarian portions of the carpels are only slightly coherent. 



H 



