DEVELOPMENT OF PLANTS 463 



arm of the lever, thus causing the long arm to swing down, 

 pressing the fertile anther upon his back and dusting him with 

 spores. Later, the style which is at first immature and above 

 this apparatus, grows out and curves down and at maturity 

 comes to lie in such a position as to rub upon the back of a 

 visiting insect at the same point as the anthers. The peculiar 

 forms of the corolla, the relation of the anthers and stigmas and 

 the frequent occurrence of hairs and bristles that direct the in- 

 sect with the greatest precision to particular parts of the flower 

 with a view to crossing, mark this family of the mints as the 

 most specialized of the order. A fine series of devices are seen 

 in such common mints as the blue curls {Trichostema) , skull- 

 cap {Scutellaria), hyssop (Agastache), ground ivy (Gleconm), 

 catmint (Nepeta), selfheal (Prunella), motherwort {Leoniirus), 

 dead nettle (Lamium), hedge nettle (Stachys), sage (Salvia), 

 bergamot (Monarda), pennyroyal (Hedeoma), mountain mint 

 (Kolleia), bugle weed (Lycopus), etc. Many of these plants 

 are of commercial importance. Mentha yields valuable oils as 

 spearmint, peppermint, and menthol and from other genera are 

 derived oils used in perfumery, medicine and as condiments, 

 as rosemary, lavender, origanum, thyme. Several are cultivated 

 for their flowers and foliage, as the coleus, monarda, stachys, etc. 

 The large family of figworts, Scrophulariaceae, with its 2,400 

 species, closely resembles the mints, but is distinguished by the 

 ovary being undivided and containing many seeds on a central 

 axis (Fig, 333, C). While the simpler forms have almost regular 

 corollas and five stamens, the higher forms are bilabiate with 

 two to four stamens as in the mints. This family contains some 

 of the most showy of our cultivated plants, as the foxglove 

 (Dasystoma and Digitalis), Gerardia, snapdragon (Antirrhi- 

 num), rattlebox (Rhinanthits) , toadflax (Linaria), Paulownia, 

 beard tongue (Pentstemon), monkey flower (Mimulus); and the 

 allied Catalpa and trumpet creeper; also many other attractive 

 plants that are not cultivated as the muUen (Verhascum), fig- 

 wort (Scrophularia), turtle head (Chelone), hedge hyssop (Gra- 

 tiola), speedwell (Veronica), painted cup (Castileja), lousewort 

 (Pedicularis), cow-wheat (Melampyrum). These plants are 



