COROLLIFLOR^ 255 



several species autogamy is impossible, while in 

 others autogamy takes place when allogamy fails. 

 The Snapdragon mentioned above bears homoga- 

 mous bee-flowers with a valvular mechanism closing 

 the throat of the corolla-tube. The anthers are in- 

 cluded and set close against the upper lip, so that 

 their pollen -grains adhere to the back of the bee, 

 which effects its entrance into the flower by forcing 

 down the closing palate. The Order is closely allied 

 to Acanthaceee, from which it is distinguished mainly 

 by the nature of the placentation, and often by the 

 absence of bracteated inflorescence. 



Nat. Order 25. Orobanchacece. — Leafless root-para- 

 sites. Stem a flowering scape. Flowers like those 

 of Scrophulariacece. Ovary i-celled, with numerous 

 ovules on parietal placentas, which sometimes meet 

 in the centre of the ovary. 



The distribution is temperate and tropical. Common 

 plants: bania-bau (Orobanche indica and O. cemua) 

 (Plate VIII, fig. b), which are leafless erect parasites 

 on the roots of Tobacco, Poppy, Mustard, Brinjal, 

 and other winter field-crops, on which they cause 

 havoc if well established; ^ginetia pedunculata 

 (Plate VIII, fig. a) is a parasite on khus-khus {Andro- 

 pogon sqtiarrosus) and other grasses. The first two 

 species have homogamous bee-flowers. 



Nat. Order 26. Utriculariacece. — Herbs growing in 

 water or damp places. Leaves when submerged are 

 divided into capillary segments bearing small bladders 

 or utricles. Flowers bilabiate; stamens 2; carpels 2, 

 connate in a i-celled superior ovary, with free-central 

 placentation. 



Distribution both tropical and temperate. Common 

 plants: different species of Utricularia (see fig. 66), 

 common in ponds and ditches and marshy places, 



