ANGIOSPERMS. ai^ 



and Trollius), or a gradual transition takes place from the sepaloid throuf^h the 

 petaloid to the staminal structure (as in Nymphaea). 



But besides the usual sepaloid and petaloid form and structure of the perianth- 

 leaves, there occur other considerable deviations from the ordinary foliar structure. 

 Thus, for example, the (imperfect) perianth of Grasses consists of very small delicate 

 colourless membranous scales (the Lodicu/es), that of some Cyperacese is replaced by 

 hair-like bristles, the Se/cE ; in the place of the calyx of Compositae a crown of 

 hairs, the Pappus, surrounds the corolla ; and it has already been mentioned that the 

 petals of Aconitum, Helleborus, &c., are transformed into nectaries of a peculiar 

 form. 



Whether the perianth consist of one or two whorls, the leaves of the same 

 whorl have very commonly the appearance of being coherent or of coalescing with 

 one another, forming a cup, bell, tube, and so forth, the number of the coherent 

 sepals or petals being determined by that of the marginal teeth. Coherent perianth- 

 whorls are produced, after the formation of the distinct foliar structures at the cir- 

 cumference of the receptacle, by the common zone of insertion of these distinct 

 structures being raised up by intercalary growth as an annular wall, and forming, as 

 it continues to develope, the part common to the whole whorl of floral leaves. 

 The coherent tubular or campanulate part does not therefore consist of originally 

 free portions which cohere subsequently by their edges, but from the very first it 

 forms a whole which is intruded, so to speak, at the base of the perianth-leaves; 

 the originally free leaves eventually forming the marginal teeth of the common 

 basal portion. Applying the term Sepal to a calycine. Petal to a corolline leaf, 

 a calyx consisting of coherent leaves is gamoscpalous or synsepalous, a corolla con- 

 sisting of coherent leaves gamopetaloiis or sympetalous ; if the leaves of the perianth- 

 whorl are not coherent, but free, this is expressed by the terms eleutherosepalous 

 or aposcpalous, and clcuthcropetalous or apopetalous^ . When there is only one 

 perianth-whorl, and it is desired to state whether it consists of coherent or of free 

 leaves, the terms gamophyllous or symphyllous and ekiitherophyllous or apophylloiis 

 may be used. It sometimes happens moreover that two perianth-whorls coalesce 

 into one, so that, for example, two alternating trimerous whorls have united into a 

 six-toothed tube (as in Hyacinthus, IMuscari, &c.). 



If the leaves of the outer and inner whorls are free (not coherent), and if 

 the distinction between calyx and corolla is clearly marked, then, in addition to 

 the structural distinctions already named, other differences of form are also usually 

 to be observed. The sepals have generally a broader base, are sessile, usually of 

 very simple oudine and pointed at the apex; the petals have mostly a narrower 

 base, their upper portion is often very broad, and a distinction is not unfrequently 

 apparent of claw {unguis) and blade (lamina), and the lamina is often divided or 

 otherwise segmented. At the point where the lamina bends back from the unguis, 

 ligular structures are often formed on the inner or upper side, which are then, when 

 treating the flower as a whole, comprised under the term Corona, as in Lychnis 



^ The terms ' polysepalous ' and ' polypetalous ' are objectionable, since these terms do not 

 express the contrast correctly : still more so are ' monosepalous ' and ' monopetalous,' as applied to 

 the coherent whorls, because Vney have no relcience to the true nature of the phenomenon. 



