292 



CLASSIFICATION 



The Traveller's Tree, belonging to the genus Ra- 

 venala, a small tree with distichous plantain-like 

 leaves, is a native of Madagascar, and is often 

 planted in our gardens. 



Nat. Order 11. Orchidacece. — Herbs, usually epi- 

 phytic in the tropics and terrestrial in the temperate 

 regions: the epiphytes with their perennial stems or 

 branches variously thickened and often forming a 

 pseudo-bulb; the terrestrial forms often tuberous- 

 rooted with annual herbaceous leafy or leafless flower- 

 ing shoots. Flowers usually showy, hermaphrodite, 

 and irregular. Perianth superior, of 6 petaloid seg- 

 ments in 2 whorls ; the 3 outer segments nearly equal, 

 of the 3 inner segments the 2 lateral ones equal, and 

 the central one larger than the other two, and known 

 as the LABELLUM or lip; the labellum is normally 

 posterior but rendered anterior by the twisting of the 

 ovary. It is to the varying size, form, and colour of 

 the perianth-segments that the striking character of the 

 Orchid flowers is due, many of them simulating the 

 appearance of insects, such as bees, butterflies, &c., 

 or assuming other strange forms. Stamen usually 

 I ; the filament of the stamen adheres to the style 

 (gynandrous), forming together the column or GYNp- 

 STEMiUM, which rises from the top of the ovary and 

 terminates in a beak known as the rostellum, above 

 which lies the single anther with usually a pair of 

 pollinia, their caudicles ending in sticky disks or 

 glands known as the retinaculum. The rostellum is 

 merely the projecting portion of the stigma hanging 

 over and concealing the receptive portion of it. Ovary 

 inferior, usually twisted, i-celled with 3 parietal pla- 

 centas bearing a large number of very minute ovules; 

 stigma usually discoid and glutinous, situated be- 

 neath the rostellum and facing the labellum. Fruit a 



