THE CALYX. 285 



indeed, supposes the observer to occupy the centre of the flower, 

 which would reverse the direction ; but the former view is gener- 

 ally adopted. The direction is frequently reversed in passing from 

 the calyx to the corolla, sometimes with remarkable uniformity ; 

 while again the two occur almost indifferently in many cases. 



503. The kind of sestivation, although often the same both in the 

 calyx and corolla, as in Parnassia (Fig. 304) and Elodea (Fig. 

 300), where both are quincuncially imbricated, is as frequently 

 different ; and the difference is often characteristic of families or 

 genera. Thus, the calyx is valvate and the corolla convolute in 

 all Malvaceae ; the calyx imbricated and the corolla convolute in 

 Hypericum, in the proper Pink tribe, &c. Solitary exceptions 

 now and then occur in a family. Thus, the corolla in Rosacese is 

 imbricated, so far as known, except in Gillenia, where it is convo- 

 lute. In general it may be said, that the sestivation of the corolla 

 is more disposed to vary than that of the calyx. 



504. The Calyx, In treating of the general structure and diver- 

 sities of the flower, we have already noticed the principal modifi- 

 cations of the calyx and corolla, as well as the terms employed to 

 designate them ; which need not be here repeated. 



505. The number of sepals that enter into the composition of a 

 calyx is indicated by adjectives formed from the corresponding 

 Greek numerals prefixed to the name, as disepalous for a calyx of 

 two sepals; trisepalous, of three sepals; tetrasepalous, of four; 

 pentasepalous, of five ; liexasepalous, of six sepals ; and so on. 

 Very commonly, however, the Greek word for leaves, phytta, is 

 used in such composition ; and the calyx is said to be diphyllous, 

 triphyllous, tetr aphyllous, pentaphyllous, hexaphyllous, &c., ac- 

 cording as it is composed of 2, 3, 4, 5, or 6 leaves or sepals re- 

 spectively. These terms imply that the leaves of the calyx are 

 distinct, or nearly so. When they are united into a cup or tube, 

 the calyx was by the earlier botanists incorrectly said to be mono- 

 phyllous (literally one-leaved) ; a term which we continue to use, 

 guarding, however, against the erroneous idea which its etymology 

 involves, and bearing in mind that the older technical language in 

 botany expresses external appearance, rather than the real struc- 

 ture, as we now understand it. The correct term, calyx gamophyl- 

 lous, is now coming into general use ; this literally expresses the 

 true state of the case, and is equivalent to the phrase sepals united : 

 the degree of coalescence being indicated by adding "at the base," 

 " to the middle," or " to the summit," as the case may be. 



