DEVELOPMENT OF PLANTS 447 



runs down through a narrow duct between the filaments and 

 collects in the spur-like prolongation of the corolla (Fig. 333, s). 



The yellow rattlebox (Rhinanthus, Fig. 333, D, E) shows an- 

 other form of the flower, common in this family. The general 

 arrangement of the floral organs is the same as in Linaria, but 

 the anthers are in pairs so that when they open, owing to the 

 rigidity of the filaments or the pressure of the upper lip, they 

 are kept tightly pressed together like a pair of sugar tongs, 

 thus preventing the shedding of the spores. Owing to the form 

 of the corolla and often because of numerous hairs and bristles, 

 the insect is directed in such a definite way to the flower that he 

 comes in contact with appendages of the anthers, or causes a 

 slight deflection of the rigid filaments or of the lip of the corolla, 

 any of which movements are sufficient to separate the anthers 

 and bring down upon him a shower of spores. These flowers 

 are largely protogynous so that at first only a crossing is possible. 

 In many species, autogamy results from the downward bending 

 of the corolla and style, accompanied by a loosening of the anthers 

 so that during the last days of flowering the spores may fall 

 directly upon the stigma. 



Many of these flowers are characterized by mottlings and 

 blotches. It appears to be a rather general law that the most 

 highly modified parts are variegated in this manner compare the 

 mints and orchids. Less specialized flowers present an associa- 

 tion of various colors or veinings, a feature that is illustrated 

 in many families as violets, peas, geraniums, etc., whereas, the 

 simplest types of flowers are usually of a uniform color. The 

 figworts have been called a suspicious group, and if not actually 

 poisonous, none at least serve as food. Several are medicinal, 

 as Digitalis, Veronica, Gratiola, etc. Many are parasitic, as the 

 foxglove, Gerardia, eyebright (Euphrasia) and the related and 

 reduced brownish rapes (Thalesia and Orobanche), beech drops 

 (Leptamnium) and squawroot (Conopholis). 



The curious family of the bladderworts is closely related to 

 the figworts. The bladderwort (Utricularia) is a very common 

 aquatic in still waters and ponds. Certain leaves become modi- 

 fied into elaborate sacs with trapdoors for enticing and capturing 



