24 BOTANY. 



ccntrlfugally. The simplest form is that of a single terminal flower. We 

 may suppose a leaf to be developed on each side of the flower, in each of 

 whose axils a new bud is produced, which, in turn, may each form the 

 centre of a tertiary development, &c. Each flower may be the centre of a 

 system of three or more instead of two. If we suppose the leaves above- 

 mentioned to be reduced to bracts, the whole forms a single inflorescence, 

 called a cynie^ this being called dichotomous or trichotomous, according to 

 the character of the subdivisions. Occasionally, in dicJiotomous divisions, 

 the flowers are developed on one side only, from which results a peculiar cur- 

 vature of the cyme, which is here called hclicoidal, or gi/rafe. 



As already remarked, the flower, except when terminal, always arises in 

 the axil of a leaf, called the bract. Leaves which arise along the floral axis 

 are called brarteoles, or hractlets. The true bract may bo variously modified 

 as to color, shape, &.c. At the base of the general umbel, in umbelliferous 

 plants, there is a whorl of bracts, termed the general involucre, that at the 

 base of the smaller umbels being called the partial involucre or involucel. 

 The cup of the acorn is produced by the union of many whorls of bracts. A 

 sheathing bract inclosing one or more flowers is called a spathe. The outer 

 sterile bracts in grasses are called glumes. 



h. The Floicer and its Appendages. 



The flower consists of whorled leaves placed on an axis, the internodes 

 of which are not developed. This shortened axis is the thalamus, or torus. 

 There are usually four of such whorls : first, an outer one called the calyx ; 

 next, the corolla ; then, the stamens ; and innermost of all, the pistil or 

 pistils. Each of these Avhorls consists, normally, of several parts. The 

 plant is called dichlamydeous, when the two outer whorls or the floral envel- 

 opes are present ; monochlamydeous, when one only exists ; achlamydeous, 

 Avhen neither is present. In most instances the Calyx and corolla, when pres- 

 ent, are readily detected ; in cases of doubt as to the true character of the 

 envelope, or when there is no convenient distinction between the two, the term 

 perianth, or perigone, may be employed. Should but one envelope be pres- 

 ent, it is always the calyx. 



The manner in Avhich the floral envelopes are folded together is known 

 as the (Estivation, or pra;floration. This is valvatc, when the elements are 

 so arranged as to constitute a circle without the overlapping of the edges. 

 Should the edges of the parts be turned outwards, the restivation is 

 reduplicate ; if inwards, induplicate. When each part of the whorl overlaps 

 the one next to it on one side, and is in turn overlapped by the part on the 

 other side, the restivation is twisted or contorted. Sometimes the elements 

 of the whorls, instead of being nearly in the same plane, stand at diff"erent 

 heights, causing an imbricated asstivation. Should the parts envelope each 

 other completely, a convolute aestivation is produced. VexiUary aestivation 

 is where one part, the vexillum of a papilionaceous flower, envelopes all the 

 24 



