BOTANY 



the Gynandrae and Burmanninese. The flowers of the Gynandrae, which com- 

 prise nearly all the Orchids, are characterized by the reduction in the number 

 of the stamens, and the complete coherence of the stamens with the style to 

 form the ' ' column " or " gynostemium " of these flowers (Fig. 373). The ovary 

 is always inferior. The flowers are strongly zygomorphic, and the posterior leaf 



of the inner perianth-whorl is 

 more or less moditied to form 

 the " Labellum " or lip of the 

 flower. By a twisting of 

 the ovary this is apparently 

 anterior in position, but occa- 

 sionally (Calopogon, Fig. 374, 

 E) it retains its primitive 

 position. In the greater num- 

 ber of Orchids (Monandrae) 

 but a single stamen is devel- 

 oped, this being the anterior 

 one of the external whorl. 

 In the Diandrae (e.g. Cypri- 

 pedium) two lateral stamens, 

 belonging to the inner whorl, 

 are developed, and the fertile 

 stamen of the other Orchids 

 is represented by a heart- 

 shaped staminodium (Fig. 

 374, F). In the Apostasieae, 

 a small family of tropical 

 Orchids, considered to be the 

 most primitive members of 

 the group, there may be three 

 perfect stamens. 



The pollen, except in the 

 lower forms, like Cypripe- 

 dium, is in waxy masses, or 

 Pollinia. These are usually 

 so placed that they can only 

 be removed by the agency of 

 insects, upon which most 

 Orchids are absolutely de- 



FIG. 373. Orchis apectabUis. A, inflorescence 

 (Xlj). B, flower with the upper part of peri- 

 anth beut back to show the column, x; L t the 

 labellum; sp, spur; o, ovary. C, the column, 

 seen from in front; an, anther; gy, stigma. 

 D, diagram of the floral parts. 



pendent for pollination. 



The ovules are usually undeveloped at the time pollination occurs, and the 

 growth of the pollen-tube is slow, sometimes requiring several months before it 

 reaches the ovules, which have been developing in the meantime. The seeds 

 are exceedingly small, and the embryo rudimentary. It is on account of the 

 small size of the seeds that these plants are known as the Microspeniiae. 



The Orchids are cosmopolitan, but are especially abundant in the Tropics, 

 especially in mountain regions. They show a greater range of habit than any 

 other order of Monocotyledons. While in cooler regions they are terrestrial, in 

 the Tropics many of them are epiphytes, and have developed special structures, 

 such as aerial roots and enlargements of the leaf-bases (" Pseudo-bulbs "), which 

 are connected with their epiphytic habit (Fig. 375). A considerable number 

 are saprophytes (e.g. Corallorhiza, Neottia, Cephalanthera, etc.), and these are 

 destitute of chlorophyll, and have their leaves reduced to scales. 



