ORCHIDE^E 663 



ORCHIDEJE. 



Benth. et Hook. Gen. PL iii. 460. 



Fruit and Seed. Ovary inferior, one-celled, with three 

 parietal placentas, or three-celled in Selenipedium, Apostasia, 

 and Neuwiedia, genera which are also markedly distinguished 

 in other respects. Ovules anatropous, minute and very 

 numerous. Fruit a membranous or coriaceous, cylindric, 

 ovoid or winged capsule, rarely fleshy, and dehiscing scarcely 

 at all or only after a time some species of Galeola, Vanilla, 

 and Sobralia, three allied genera usually dehiscing by three 

 or six longitudinal slits, with the valves cohering for some 

 time or altogether at the apex or base, or finally spreading 

 from the apex or entirely disappearing. 



Seeds very numerous, minute, more or less cylindrical or 

 spindle-shaped or tapering at one or both ends ; testa thin- 

 celled and transparent, yellow, green or brown, and very 

 loosely enveloping the embryo. There is great variety in form, 

 size, colour, and the configuration of the cells of the testa. 

 Barely is the testa winged, fitting close to the embryo from 

 which it radiates in rows, of delicate, transparent, brownish 

 cells as in Epistephium, Erythrorchis, and Cyrtosia. Vanilla 

 is also exceptional in having a crustaeeous, dark reddish-brown, 

 opaque testa. There is no endosperm. The embryo is in the 

 centre or somewhat above the centre of the seed, globular, 

 ellipsoid or ovate in shape, and represents a very low stage of 

 development, showing before germination no trace of radicle 

 or cotyledon. There is, however, a certain physiological dif- 

 ferentiation, for the longer axis of the embryo corresponds to 

 the ascending axis of the young seedling. 



The seeds show a great resemblance to those of many 

 parasites of dicotyledonous Orders, especially Orobanche, but 

 most strikingly, as Beer points out, to those of species of 

 Pyrola. 



Germination. Owing to the low stage of development of 

 the embryo in the ripe seed, only trifling differences of form 

 and colour occur in the most different genera and groups. 



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