37 



VIII. DESCRIPTION OF GENERA AND SPECIES 

 Family ORCHIDACEiE Lindl. 



The Orchidaces belong to the Monocotyledons (plants with only one seed-leaf and 

 parallel leaf-veins), and form part of the minute-seeded Microspermas, 



The flowers are hermaphrodite, with both pollen-bearing and seed-bearing organs 

 in the same flower, irregular, ^ zygomorphic,- situated above the ovary, usually 

 resupinate.3 The perianth consists of three sepals, and alternate with them two petals 

 and a labellum or lip, generally larger and more conspicuous, very often 3-lobed, 

 frequently spurred. In the centre of the flower is the column or gynostemium (formed 

 by the fusion of stamens and style into a solid body), usually facing forwards or 

 downwards. The number of anthers and stigmas differs in the two sub-families. In 

 the Diandras there are two fertile anthers, one on each side of the column at the base 

 of the lip, containing pollen in single grains immersed in 

 an adhesive paste, a large petaloid staminode terminating 

 and protecting the column, and tliree united dry non- 

 viscous stigmas, all functioning as receivers of pollen. 



In the Monandrje there is only one fertile anther, at the 

 apex of the column, containing two (rarely four or eight) 

 pollinia, built up of tetrads, i.e. pollen-grains coherent in 

 fours (except in Cephalanthera, in which they are single); 

 two stigmas functioning as such, united or separate; and a 

 rostellum or apparatus for affixing the pollinia to insects 

 (evolved from the third stigma). In some species two 

 small staminodes (vestiges of suppressed anthers) are pre- 

 sent, one on each side of the column at the base. Beneath Z 

 the perianth in both sub-families is the ovary, apparently Text-fig 7. i. Diagram of the 



- 1 11 Monandra:. 2. Diagram of the 



formed of three fertile and tliree sterile carpels, usually Diandra;. i.s. Lateral sepal. u.s. 

 unflocular (i-ceUed), bearing innumerable minute ovules ""^^^r.^:"- „, %^ ,f^;,^J: 

 (young unfertilised seeds) on three usually forked low -f- Staminode. From icomgraphie 



., /-ii NT->- 111- 1 '^^^ Orchidies d'Eiirope, by permis- 



ridges (parietal placentae), ir^ruit a dry dehiscent capsule sion of Mile A. Camus. 

 opening by the separation (except at the base and apex) 



of the valves from the intervening ridges, leaving slits through which the seeds 

 escape, either shaken out by the wind, or in certain exotic orchids "scattered by 

 the aid of elater-hke hairs developed on the interior of the valves, the movements 



I Except in a few exotic species. 



* Only divisible into symmetrically similar halves in one plane, down the middle from back to front. 



3 Reversed by twisting of the ovary or its stalk, placing the originally upturned lip downwards. 



