526 DICOTYLEDONES. 



568) which play a part in the pollination, the probosces of the 

 insects, being forcibly pushed against them, agitate the anthers and 

 shake out the pollen-grains. Capsule with loculicidal dehiscence. 

 Euphrasia (Eye-bright), Melampyrura (Cow-wheat), Rhinanthus 

 (Yellow-rattle), Odontites (Bartsia), Pedicularis (Louse- wort), and 

 Lathrcea (Tooth- wort) all have native species. The last named 

 is pale yellow, or reddish (without chlorophyll) ; it is a parasite on the 

 roots of the Hazel, Beech and other shrubs, having an serial stem, and an 

 underground, perennial rhizome, covered with opposite, scale-like, more or less 

 fleshy leaves with a number of internal glandular, labyrinthine cavities. The 

 inflorescence is a unilateral raceme. It approaches Gesneriacece in having a 

 unilocular ovary with two parietal placentae. 



FIG. 568. Euphrasia officinalis. Flower of the large and the small-flowered forms; 

 showing the anthers and stigmas. 



The mechanical contrivances for POLLINATION are so numerous that no 

 general principle can be laid down. Personate flowers, like those of Antir- 

 rhinum are only accessible to strong insects, such as humble-bees, which can 

 force themselves between the two lips, and so become dusted with pollen on 

 the back. In Euphrasia and other Ehinanthece the insects become covered with 

 smooth, powdery pollen when they shake the anther-apparatus in touching the 

 hairs and bristles mentioned above. Scrophularia nodosa is protogynous (Fig. 

 565). Digitalis purpurea, however, is protandrous. Mimulus luteus and some 

 others have sensitive stigmatic lobes, which shut up on being touched. The 

 Fmmica-species constitute a series, from large-flowered down to small-flowered 

 forms, and parallel with them are found various gradations from insect- to self- 

 pollination. In some (as Euphrasia officinalis, Rhinanthus crista galli) there 

 are two kinds of flowers : large, which are pollinated by insects, and small, 

 which arc self -pollinated (Fig. 5G8). Lathrcea squamaria (Tooth- wort) is a pro- 

 togynous spring-flowering plant, largely visited by humble-bees. Others have 

 cleistogamic flowers. Nycterinia capensis opens its flowers at night. 



