43 



coloured perianth leaves and attractive scents. From this we 

 see that, however conspicuous the perianth leaves of a flower 

 may be, these are after all of only subsidiary importance and 

 that the really essential organs of a flower are the stamens and 

 pistils, without which no seed can be formed. There are 

 indeed some flowers which only contain each a single pistil, 

 or a single stamen, but which nevertheless must be regarded 

 as true flowers. 



39. The perianth of a flower Perianth ' 



may consist of leaves which are all alike, or it may consist of 

 two distinct sets of leaves, the outer of which are usually 

 green and the inner of more delicate texture, and, being white, 

 or of some colour other than green, the latter serve to make 

 the flower conspicuous. The former are called sepals and 

 together constitute the calyx, the latter are the petals and 

 together constitute the corolla. In Rosa, moschata for instance, 

 we find no difficulty in distinguishing the inner 5 large white 

 petals from the outer green sepals. 



A flower which has both sepals and petals is said to be 

 dichlamydeous, one which is without both sepals and petals, 

 i.e. with no perianth, is achlamydeous, while one which has 

 only sepals, or only petals, is monochlamydeous. A flower 

 which has no petals is also said to be apetalous. When the 

 perianth leaves are all similar and there is therefore no 

 obvious calyx and corolla, the leaves are merely called perianth 

 leaves. If they are all coloured like petals the perianth is 

 said to be petaloid, whereas if they all resemble sepals the 

 perianth is sepaloid. If the perianth, calyx, or corolla, of a 

 flower consists of distinct leaves, which are separate from one 

 another and each of which has a distinct insertion of its own 

 upon the receptacle, the perianth, calyx, or corolla, respectively, 

 is said to be polyphyllous, polysepalous, or polypetalous. On 

 the other hand a 'perianth, calyx, or corolla, of united, or 

 connate, leaves, is said to be gamopliyllous, gamosepalous, or 

 gamopetalous. According to the degree of cohesion between 

 the respective perianth leaves, sepals, or petals, they are 

 said to be connate at the base, to or beyond the middle, nearly 

 to the apex, and so on. 



In cases of cohesion, where there is a distinct narrow base 

 formed by the lower connate portions of the leaves, this is 

 called the perianth-, calyx-, or coiolla-tube and the upper 

 expanded portion is called the limb. The intermediate portion, 

 usually slightly more expanded than the tube and not so much 

 expanded as the limb, is called the throat. The calyx or 



