136 
ORGANOGRAPHY. 
BOOK I. 
series is the calyx. A calyx, therefore, can exist without a 
corolla ; but a corolla cannot exist without a calyx. 
The term Perianth is sometimes given as synonymous with 
calyx ; but this is an error. 
The word Perianth signifies the calyx and corolla com- 
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 caljrx and corolla 
exist, and by the usual origin of those parts in two distinct 
whorls), the utility of the term Perianth is rendered ex- 
tremely 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 Can- 
dolle, have substituted Perigonium for Perianthium : but the 
latter is in most common use, its application is perfectly 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terms is obsolete.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 (sepala) ; a 
term first invented by Necker, and recently revived by De 
Candolle. Botanists of the school of Linnaeus call them the 
leaflets or foliola. Link says the word sepalum is barbarous, 
and proposes to substitute phi/Hum. 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 
