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. 

 Euplvrasia (Eye-bright), Melampyrum (Cow-wheat), RhinantJuis 

 (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 tbe Hazel, Beech and other shrubs, having an serial stern, 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 

 unilocu-Jar ovary with two parietal placentae. 



FIG. 568. Eiiphrnsirt offlclnalis. 

 showing the anthers and stigmas. 



Flower of the large and the small-flowered forms ; 



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 Euplimxia and other Rhinantltece the insects become covered with 

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

 hairs and bristles mentioned above. Scraphularia iiodoxa is protogyuous (Fig. 

 565). Digitalis purpurea, however, is protandrous. Mimuliix liiteus and some 

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

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

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

 pollination. In some (as Euphra<ia officinalis, IHiiiianthu* criata galli) there 

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

 which are self-pollinated (Fig. 568). Latliraa sqnamaria (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. 



