INTRODUCTION 
though they may be notched more or less deeply, as in the Rose, which is 
termed emarginate , or the Chickweed, which is bi-fid, fringed, as in Pinks, or 
deeply multi-fid , as in Mignonette, or cut up in a branching manner, or 
laciniate , as in Ragged Robin. “ Double ” flowers, with more than one 
whorl of petals, are rare in a wild state ; and three, four, or five are the 
most usual numbers. The presence or absence of cohesion between the 
petals, whether, that is, they are polypetalous or gamopetalous , is an important 
character in classification ; as is also their insertion, whether hypogynous , 
perigynous , or epigynous ; and their symmetry. 
The chief polypetalous forms demanding separate consideration are 
the cruciform , characteristic of the Family Crucferce, which includes 
Wallflower, Mustards and Cresses, in which there are four equal petals 
placed cross-wise, or, as it is put technically, in the diagonal planes, in one 
whorl ; and the papilionaceous (Latin papilio, a butterfly), characteristic of 
all the British representatives of the Pea and Bean Family ( Leguminosce ), in 
which there are five petals, the posterior one — that nearest the stem — 
called the standard and usually the largest and most erect, two side ones 
called wings , and two lower or anterior, often slightly united, known 
as the keel , the whole corolla being thus monosymmetric, or divisible 
symmetrically only along one plane, that known as the median plane , 
extending from the back to the front of the flower. 
Among gamopetalous corollas the chief polysymmetric forms are the 
tubular , as in the florets of Thistles ; the wider bell-shaped or campanulate , 
as in the genus Campanula , including the Hare-bell ; the urceolate , or 
barrel-shaped, narrowing at the mouth, as in many Heaths and Whortle- 
berries ; the funnel-shaped, narrow at the base and widening outwards, as 
in the small Field Convolvulus ; the trumpet-shaped , with reflexed margins, 
as in the large Hedge Convolvulus ; the salver-shaped , with long tube and 
limb at right angles to it, as in the Primrose ; and the rotate or wheel- 
shaped, with short tube, as in the Pimpernels and Forget-me-not. The 
chief monosymmetric gamopetalous forms are the bi-labiate and the 
ligulate. The bi-labiate or two-lipped corolla has generally two posterior 
petals united to form the hood and three anterior ones united into a 
XXXVI 
