450 



EXOGENOUS OR DICOTYLEDONOUS PLANTS. 



843. Ord, Hydroleaceffi differs (not sufficiently) from the last by 

 the simple and entire leaves, the two-celled ovary, 'the two distinct 

 styles, and the numerous seeds. Ex. Hydrolea, Nama : chiefly 

 natives of warm regions. 



844. Ord, Polemoniaceae (the Polemonium Family}. Herbs, with 

 alternate or opposite leaves, and panicled, corymbose, or clustered 

 flowers. Calyx five-cleft. Corolla regular, with a five-lobed limb, 

 convolute in aestivation. Stamens five, inserted on the corolla 

 alternate with its lobes, often unequal. Ovary free, three-celled, 

 with a thick axis, bearing few or numerous ovules : styles united 

 into one : stigmas three. Capsule three-valved, loculicidal ; the 

 valves also usually breaking away from a thick central column 

 which bears the seeds. Embryo straight, in fleshy or horny albu- 

 men. Ex. Polemonium (Greek Valerian), Phlox, Gilia. Chiefly 

 North American ; many are very common ornamental plants in 

 cultivation. 



902 



845. Ord, Diapensiaceae, Low, prostrate, and tufted suffruticose . 

 plants ; with crowded and evergreen heath-like leaves, and solitary 

 terminal flowers. Differing from the last family chiefly in tlw 

 transversely two-valved anthers, and amphitropous seeds. Con- 



FIG. 902. Flowers of Polemonium. 903. Flowers of Phlox. 904. Corolla of the same laid 

 open, showing the stamens unequally inserted on its tube. 905. Pistil of the same. 906. Cross- 

 section of the capsule of Polemonium. 907. Cross-section of a magnified seed. 911. Perpen- 

 dicular section of the same. 912. Magnified embryo. 908. Cross-section of the dehiscent cap- 

 sule of Collomia. 909, 910. Capsule of Leptodactylon. 



