FAMILIES OF FLOWERING PLANTS. 6^ 



disk or gland. The ovary is inferior, its tube united with that of the 

 perianth, 3-angled, and often twisted, thus altering the natural position 

 of the flower. These features are shown in figure 54. 



The family contains 410 genera and 5000 species, of wide distri- 

 bution, but most abundant in the tropics. Probably no group of 

 flowering plants yields a larger number of species valuable for green- 

 house cultivation as ornamental plants. Representatives of nearly all 

 the important genera may be found in every large orchid house. The 

 most economic product of the family is vanilla, which is obtained from 

 the fruit of the climber Vanilla pJiinif alia and from several related 

 species. The common putty-root [Ajdectrum hyemale) of the eastern 

 United States is said to furnish a valuable cement; while the substance 

 known as sales is derived from the roots of the European species 

 OrcJiis mascvla. The genera which are important as yielding the 

 most beautiful flowers in cultivation are Cyprl])ediurii^ Cattleya, 

 LaeJia, Oucidium, Odontoglossum^ and Lycaste. With the exception 

 of the first, these are all exotics; but some of our native Cypripediums 

 have flowers of great beauty. Figure 55 shows a cluster of the yel- 

 low ladies' -slipper {C. Iiirsutum). Other native orchids of great 

 beauty are Calypso, of the northern peat-bogs; Llmodorum and Po- 

 gonia, the grass-pinks; various species of Ilahtmaria, with pink, pur- 

 ple, orange or white flowers; and the delicate white ladies' tresses 

 {^Gyrostachys). The reader is referred to various popular works for 

 more extended descriptions of our native orchids, as it is impossible to 

 admit extended details into this brief review of the plant families. 

 For a full discussion of the peculiar modes of fertilization no work is 

 more valuable than Darwin's "Fertilization of Orchids," while several 

 essays on this subject in the works of William Hamilton Gibson will 

 be found most interesting. 



