4o8 



THE ORCHIDALES 



leaves have also become reduced to mere scales and the chloro- 

 phyll has disappeared. The organs of the flowers are subject to 

 such remarkable variations that the various parts may appear at 

 first somewhat difficult to recognize. It is evident that the same 

 line of variation noted in the higher families of the Liliales has 

 been continued, for the perianth is arranged upon a compound 

 ovary, but its parts are often sharply differentiated into calyx 

 and corolla. The sepals and petals comprising these two whorls 

 differ greatly in form, but especially to be noted is the oddly con- 

 structed petal known as the labellum (Figs. 292, 293, /). This 

 organ is the most striking feature of the orchid and it assumes 



Fig. 292. A simple type of the Orchidales: A, the moccasin flower, Cy- 

 pripedium — /, labellum; p, the two unmodified petals; 5, sepals, two being 

 united below the labellum; b, bract, partially concealing the inferior ovary. 

 B, section of the flower — /, labellum; s, stigma; an, anther; st, shield-like 

 sterile stamen covering the two anthers and stigma; 0, ovary; b, b'ract. 



an almost endless variety of forms and colorations, being a good 

 illustration of Wallace's law that the most highly modified part 

 shows the greatest variation in coloration. In Cypripedium (Fig. 

 292, A) the labellum assumes the form of a mocassin, in other 

 genera it resembles a vase, boat, tongue, body of insect, etc. It 

 is entire or variously lobed, slit, fringed and often prolonged into 

 a tube for the concealment of nectar. The stamens and stigmas 

 are reduced in number and greatly modified, the former organs 

 usually being reduced to one and so fused with the style that the 



