FLOWERS AND THEIR WORK. 221 



flower-bud than a polysepalous one, but also gives support and protec- 

 tion to the base of the adult flower and to the developing fruit. Hence 

 the gamosepalous calyx never falls off when the flower is young. In 

 " Winter Cherry" the calyx forms a red bladder round the fruit. 



When the flowers and fruits are closely aggregated, they no longer 

 need a protective calyx, which therefore becomes quite small, as in 

 Umbellifers, and when a closely packed mass of flowers is surrounded 

 by a ring of protective bracts, the calyx may either disappear (Daisy) 

 or be represented only by hairs. These hairs in the Dandelion, Thistle, 

 Hawk weed, etc., persist after flowering, and f orm a pappus, which ia 

 attached to the ripened fruit and aids in its dispersal by the 

 wind. 



The sepals are usually green, but the "petaloid" sepals of Monks- 

 hood, Winter Aconite, Christmas Rose, Larkspur, and Marsh Marigold 

 are brightly coloured, and take on the attractive function of the 

 petals, which are either developed as nectaries or are absent. 



Examine and sketch (1) the entire calyx, (2) the individual sepals, 

 of the following flowers : Buttercup, Lesser Celandine, Wallflower, 

 Sweet Pea, Gorse, Mallow, Rose, Cinquefoil, Strawberry, Cherry, 

 Dead-nettle, Foxglove, Larkspur, Monkshood, Christmas Rose, 

 Winter Aconite. 



253. Corolla. The primitive corolla consists of a spiral of free 

 petals, but in most plants this has been changed into a single whorl 

 (Foxglove, Geranium) or, more rarely, a double whorl of petals 

 (Poppy). The corolla protects the stamens and carpels at the most 

 critical period of their existence, and this is especially the case when 

 the petals have grown together to form a tube enclosing the essential 

 organs. The corolla-tube often serves as a receptacle for honey, while 

 the coloured portion attracts the visits of insects. As soon as fer- 

 tilisation has occurred, the seeds begin to develop, and an attractive 

 corolla being no longer needed, it is usually rapidly shed. The 

 withered corolla may, however, persist round the fruit (e.g. Heaths, 

 Plantains, Clover). 



When the corolla is polypetalous, the individual petals often consist 

 of a narrow stalk or claw, and an upper broader portion, the blade 

 or limb (Wallflower). The petals of the Pink have a scaly outgrowth 

 (ligule) at the junction of the claw and limb, and in Narcissus there is 

 a circular cup, or corona. 



The corolla is said to be regular when all its parts are similar, 

 irregular when they differ in shape from one another, and the same 

 terms apply whether it is poly- or gamopetalous. In Christmas Rose 

 and Winter Aconite the petals are represented by hollow nectaries, 

 and the sepals form the showy attractive portion of the flower. The 

 nectaries are represented in the Buttercup by tiny pockets placed 

 behind a scale at the base of the inner surface of each petal. Hence 

 the nectaries of the Christmas Rose are probably modified petals, as are 

 undoubtedly the two posterior ones of the Monkshood. 



Examine and sketch (1) the entire corolla, (2) the individual petals 

 if free, of the flowers mentioned in Art. 252. 



