290 CHANGES IN STYLE AND STIGMA. 



insect touches the back of the keel, -which throws itself hastily back- 

 ward, and the insect receives a few grains of poUen, with which it 

 impregnates a neighbouring flower. In Fumariaceee the stamens and 

 pistil are enclosed between two petals. At the base of the petals, 

 which is prolonged into a spur, there is a quantity of nectar which 

 attracts insects. To reach this an insect must pass between the two 

 petals, the uppfer parts of which, being borne upon a sort of hinge, 

 separate easily ; then the insect is covered with pollen, which is 

 applied to the stigma. 



Hermann Miiller states that there are two forms of Euphrasia offici- 

 nalis in which the mode of fertilisation is different. In the large 

 form there is provision for insect fertilisation or cross-fertilisation; 

 while in the smaller-flowered form there is regularly self-fertilisation. 

 In Rhinanthus Cristar-galli there are also two forms, one small and the 

 other large. In the former there is self-fertilisation, whUe in the 

 latter this is not the case, as the stigma so far overlaps the anther 

 as to render self-fertilisation impossible. 



Other animals, besides insects, are instrumental in distributing 

 pollen. Humming-birds, when inserting their bills into the nectaries 

 of plants in some countries, carry the pollen on their head feathers from 

 one flower to another. They are said to act as pollen-distributors in 

 the case of a species of Erythrina in Nicaragua. In Marcgraavia 

 nepenthoides there are peduncular pitchers below the flowers con- 

 taining a sweet liquid, attracting insectivorous birds which come and 

 feed on their contents, and in so doing burst the anther and carry 

 the pollen to other plants. 



WhOe the pollen is being elaborated, the stigma is also under- 

 going changes. It becomes enlarged, and secretes a viscid, usually 

 saccharine, matter, ready to detain the poUen-grains when they 

 are discharged. In Goldfussia anisophylla, and in species of 

 Campanula, as C. media, C. Eapunculoides, 0. Trachelium, 0. 

 rotundifolia, the style is covered with collecting hairs (fig. 

 516), which appear to aid in the application of the pollen. 

 In the first-mentioned plant a remarkable curvation of the 

 style takes place, so as to mak« the stigma come into contact 

 with the hairs. In Campanula the style is at first slightly 

 longer than the stamens, but it soon becomes twice their 

 length, and during its elongation the hairs upon it brush the 

 pollen-grains out of the anther-eases. The stigma consists of 

 two branches, which are at first erect and closely applied to 

 Fig^ie ^^^^ other, but afterwards, by changes in the cells, become 

 revolute. This completely developed state of the stigma does 

 not occur until some time after the poUen of its own flower has been 



Fig. 616. Style of a species of Bellflower {Camiianula), covered with liaixs, which brash 

 out the pollen from the anthers. 



