Order 1. =Burmanniaceæ.= This order forms a transitional link between the Gynandræ and the epigynous Liliifloræ (_Amaryllidaceæ_), in having a 6-leaved perianth, and 6–8 stamens; but some have a labiate perianth (the median perianth-leaf of the _outer_ whorl being very large). The ovary is most frequently unilocular with three parietal placentæ; but in some it is 3-locular with axile placentation. Capsule. Seeds ∞, small, with _endosperm_. The relationship to the Orchidaceæ is shown especially in the very imperfectly developed embryo and in the ovary. Small, tropical herbs (59 species); some are saprophytes. [Illustration: FIG. 318.--_A_ Diagram of an Orchid-flower. _B_, _Cephalanthera_. Stylar-column: _a_ anther; _s_ stigma; at the foot are seen scars indicating the position of the parts which have been removed.] Order 2. =Orchidaceæ.= The epigynous, petaloid perianth is strongly zygomorphic in having the _posterior_ leaf of the interior whorl, the _lip_ (labellum), differing from all the other leaves in form, size, and colour (except _Apostasieæ_); the position of the labellum is very frequently reversed, being turned _forwards and downwards_ by the twisting of the ovary (Fig. 318 _A_). _Only_ 1 of the stamens--the anterior of the external whorl--is developed and bears an anther (by the twisting of the ovary it is turned posteriorly and upwards); the others are entirely wanting (indicated by * in Fig. 318 _A_) or present as staminodes (Fig. 318 _A_, δ δ) (except _Apostasieæ_, _Cypripedileæ_); the filaments are united with the style to form a column (Fig. 318 _B_), the _stylar-column_[30] (_gynostemium_), and the anther (_a_) is thus placed on its apex and exactly behind or over the stigma (_s_). The anther is 4-locular; the pollen-grains do not separate (except _Apostasieæ_, _Cypripedileæ_) but remain united either in tetrads or in masses, which correspond to a pollen-mother-cell (Fig. 320 _C_, _D_, _E_); or the pollen-grains, formed in each of the two anther-halves, remain united and form one or a few wax-like masses (pollen-masses, pollinia). The 3 carpels form a _unilocular ovary_ with 3 parietal, deeply bifid placentæ (except _Apostasieæ_, _Selenipedilum_). Only the two lateral carpels are prolonged and developed into the stigma (Fig. 318 _B_, _s_), while the one lying in the median line, which is situated just within the anther (Fig. 318 _A_), becomes either rudimentary or developed into the “_rostellum_” (“a small beak”), on which the sticky bodies (_glandulæ_) arise; by aid of these the heavy, connected pollen-masses may be glued to the insects which visit the flower, and pollination is thus secured (in _Apostasieæ_ and _Cypripedileæ_ the 3 carpels each contribute to the formation of the stigma). The fruit is a _capsule_ which most often dehisces _by 6 valves_, 3 of which are broader and bear the placentæ, and 3 alternating with them are narrower and barren (except _Vanilla_).