STRUCTURE.] SEPALS. 327 



bined, and is therefore strictly a collective term. It should 

 only be employed to designate a calyx and corolla, the limits 

 of which are undefined, so that they cannot be satisfactorily 

 distinguished from each other, as in most Monocotyledonous 

 plants, the Tulip and the Orchis for example. But since, 

 even in such plants as these, there can be no reasonable doubt 

 that the three outer floral leaves are the calyx, and the three 

 inner the corolla (as is shown both by Tradescantia and its 

 allies, in which the usual limits between calyx and corolla 

 exist, and also by the usual origin of those parts in two 

 distinct whorls), the utility of the term Perianth is rendered 

 extremely confined. It is often a mere evasion of the task 

 of ascertaining the exact nature of the floral envelopes in 

 doubtful cases. Some writers, among whom are Link and 

 De Candolle, have substituted Perigonium for Perianthium : 

 but the latter is in most common use, its application is well 

 understood, and there is no good reason for its being changed. 

 Ehrhart, with whom the name Perigonium originated, called 

 it double when the calyx and corolla are evidently distinct, 

 and single if they are not distinguishable : but this use of 

 terms is obsolete. 



The divisions of a calyx are called its sepals (sepald) ; a 

 term first invented by Necker, and revived by De Candolle. 

 Botanists of the school of Linnseus call them the leaflets 

 or foliola. Link says the word sepalum is barbarous, and 

 proposes to substitute phyllum. The sepals are generally 

 longer than the corolla in aestivation, and during that period 

 act as its protectors : during flowering they are mostly 

 shorter. 



The calyx, in ordinary cases, if deciduous, falls off from the 

 peduncle by its base. In many cases the sepals drop off 

 separately, as leaves fall from the stem ; but occasionally they 

 cohere firmly into a sort of cap or lid, which is pushed off 

 entire by the increase of the corolla and stamens : in these 

 cases the calyx is said to be operculate, if it falls off without 

 any lateral rupture of its cap, as in Eucalyptus ; and calyp- 

 trate, if at the period of falling it bursts on one side, as in 

 Eschscholtzia. In the former of these two cases, the cohesion 

 between the sepals is complete and never destroyed ; in the 



