MONOCOTYLEDONS AND DICOTYLEDONS 



249 



cies of Iris (flags) (Fig. 232), Crocus, Gladiolus (Figs. 233, 

 234), etc., the flowers are not only epigynous, but some of 

 them are zygomorphic. 

 When a plant has 

 reached both epigyny 

 and zygomorphy in its 

 flowers, it may be re- 

 garded as of high rank. 



136. Orchids.— In 

 number of species this 

 (Orckidacece) is the 

 greatest family among 

 the Monocotyledons, 

 the species being vari- 

 ously estimated from 

 six thousand to ten 

 thousand, representing 

 between one third and 

 one half of all known 

 Monocotyledons. In display of individuals, however, the 

 orchids are not to be compared with the grasses, or even 

 with lilies, for the various species are what are called " rare 

 plants" — that is, not extensively distributed, and often 

 very much restricted. Although there are some beautiful 

 orchids in temperate regions, as species of Habenaria (rein- 

 orchis) (Fig. 235), Pogonia, Calopogon, Calypso, Cypripe- 

 dium (lady-slipper, or moccasin flower) (Fig. 236), etc., 

 by far the greatest display and diversity are in the tropics, 

 where many of them are brilliantly flowered epiphytes 

 (Fig. 237). 



Orchids are the most highly specialized of Monocoty- 

 ledons, and their brilliant coloration and bizarre forms are 

 associated with marvelous adaptation for insect visitation 

 (see Plant Relations, pp. 134, 135). The flowers are epigy- 

 nous and strongly zygomorphic. One of the petals is re- 

 markably modified, forming a conspicuous lip which is 



Fig. 230. Diagrammatic cross-section of ovary 

 of Lilium Philaildphicttm, showing the three 

 loculi. in each of which are two ovules (mega- 

 sporangia); A, ovule; B, integuments; C, nn- 

 cellus ; B, embryo-sac (megaspore).— Cald- 

 well. 



