ORCHID COLLECTING STANDLEY 365 



A similar case of symbiosis occurs in the case of the species of 

 Coryanthes (pi. 6, fig. 2), which are sometimes called bucket orchids, 

 because of the curious form of their flowers. The species figured, 

 which grows on the hills back of Panama City, has clear yellow 

 flowers, which exhibit most remarkable modifications during the 

 process of fertilization. In Coryanthes the huge masses of roots 

 are inhabited by innumerable small ants that are among the fiercest 

 of those found in Panama. So disagreeable is the process of collec- 

 tion that it is almost impossible to obtain the plants, it being stated 

 that the only practical method is to pull the masses from the tree 

 with a rope, then drag them by the rope to a stream, where they may 

 be immersed until the ants have departed. Many similar cases of 

 symbiosis between ants and orchids exist in Central America. The 

 same conditions occur also in numerous other groups of unrelated 

 tropical plants, some of which have special organs for the accom- 

 modation of their inhabitants. 



Among the vines that cover the trellises in the Powell garden are 

 various plants of Vanilla, of which there are two common species 

 in Panama, V. planifolia (pis. 16, 17) with narrow leaves and V. 

 pompona with wide leaves. There are several other species of 

 Vanilla in Central America. All are vines which climb high in the 

 trees by means of aerial rootlets, but also root in the ground. The 

 plants are usually plentiful in the lowland forests, and are found 

 almost everywhere about the Canal Zone. 



Vanilla is the only orchid with any important economic appli- 

 cation. Although so common wild in Central America, it is not 

 grown upon a commercial scale, unless it be in Guatemala, but it is 

 often planted in gardens as a curiosity. The commercial article is 

 obtained chiefly from Mexico, Tahiti, and the East Indies, but some 

 of the vanilla upon the market is an artificial synthetic preparation. 

 The flowers of Vanilla are rather showy. The natural commercial 

 substance is obtained from the seed pods. When these are dried the 

 vanillin, the aromatic principle, crystallizes on the outside of the pod. 



One of the most remarkable of Panama orchids is Selenipedium 

 chica, discovered in the mountains many years ago by Duchassaing, 

 who reported that the seed pods yielded a flavoring substance 

 similar to vanilla. It was only a few years ago that this species 

 was rediscovered, by Mr. Ellsworth P. Killip, upon Ancon Hill, 

 where, however, it is no longer to be found. The plant readies a 

 height of 15 feet, and is said by Ames to be the tallest orchid known. 

 The flowers are not very conspicuous, but somewhat resemble those 

 of the lady's-slipper of the United States. 



Among the finest of the orchids cultivated by Mr. Powell are sev- 

 eral species of Sobralia (pi. 2, fig. 2). They are terrestrial plants, 

 usually forming dense clumps containing numerous stems. The large 



