540 PHANEROGAMS, 



gamopetalous, the parts of the corona also coalesce, as in Narcissus, where it is 

 very large. 



The whole form of the perianth, especially when its structure is decidedly 

 petaloid and its dimensions considerable, always stands in a definite relation to pol- 

 lination by the aid of insects [or birds] : and large, brilliantly coloured, odoriferous 

 flowers only occur where the fertilisation is brought about by this means. The 

 purpose of these properties is to attract insects to visit the flowers ; and the in- 

 finitely varied and often wonderful form of the perianth is especially adapted 

 to compel certain positions of the body and certain movements on the part of 

 insects of a definite size and species when searching for the nectar, by which the 

 conveyance of pollen from flower to flower is unintentionally accomplished by 

 them. We shall recur in detail to these physiological questions in the Third Book. 

 The radial or bilateral symmetry of the perianth is usually associated with that of the 

 other parts of the flower, and will therefore be discussed in connection with it. 



Besides the perianth in the narrower sense which we have hitherto considered, 

 there are often additional envelopes to the separate flowers. In the Malvaceae and 

 some other plants the true calyx appears to be surrounded by a second calyx 

 {Epicalyx or Calyculus)^ the morphological significance of which, however, varies. 

 In Malope irifida, for example, the three parts of the epicalyx represent a sub-floral 

 bract with its two stipules; in Kitaibelia vzti/olia, the six-parted epicalyx consists 

 (according to Payer) of two such sub-floral leaves with their four stipules. Again, 

 the epicalyx may be purely illusory from the production of stipular structures by 

 the true sepals, as in Rosa and Potentilla. In Dianthus Caryophyllus and some 

 other species a kind of epicalyx results from two decussate pairs of small bracts 

 which are found immediately beneath the calyx ; in the terminal flowers of Anemone 

 a whorl of bracts stands at a short distance below the flower, which takes the 

 form in the nearly allied Eranthis hyemalis of a kind of epicalyx ^ The epicalyx of 

 the small flowers of Dipsacaceae is of special interest, each of them being surrounded, 

 within the crowded inflorescence, by a membranous tube, which here forms the 

 epicalyx. Sometimes, after the perianth and sexual organs have begun to be formed, 

 an outgrowth of the flower-stalk, at first annular, is formed below the flower, growing 

 up afterwards in the form of a cup or saucer, and bearing scaly or spiny protuberances. 

 A structure of this kind is called a Cupule ; and the cup in which the acorn of the 

 various species of Oak is seated is of this nature ^ In this case the cupule surrounds 

 only one flower, in the Sweet- Chestnut and Beech on the other hand it encloses a 

 small inflorescence. This spiny cupule afterwards splits from above, separating into 

 lobes, to allow the escape of the fruit which has ripened within it. When an 

 inflorescence is surrounded by a peculiarly developed whorl or rosette of leaves, as in 

 Umbelliferse and Compositse, this is called an Involucre; when a single sheathing leaf 

 envelopes an inflorescence springing from its axis, it is a Spathe. Both involucre and 

 spathe may assume a petaloid structure, the former, for example, in Cornus florida^ 

 the latter in Aroidese. 



^ [The garden Clematis known as ' Lucie Lemoine ' possesses a well-marked seven-leaved 

 involucre which has evidently originated from the growth of the axis above the outermost whorl 

 of the multiplied petaloid sepals.] 



^ On the development of the acorn-cup see Hofmeister, Allgemeine Morphologic, p. 465. 



