19 



functions of the sepals and petals are undoubtedly chiefly pro- 

 tective, preserving the essential organs from injury, but in some 

 species they also serve as attractions to insects that assist in the 

 fertilisation. 



THE LABELLUM. 



To describe the various forms which this organ assumes would 

 alone require a volume, for not only do the genera differ widely 

 in the lip character, but even the species in one genus are found 

 with such different formations that they often appear totally dis- 

 tinct from their nearest relatives. The simplest form is that of 

 Paxtonia rosea, already noticed, and, starting from that, we get 

 innumerable variations, gradually advancing in peculiarity of 

 structure, in every conceivable direction. Dendrobium Bry- 

 merianum (Fig, 5) affords an instance of a most strangely divided 

 lip, the substance very deeply cut into fine segments, giving a 

 broad fringe of twisted filaments of a most striking appearance. 

 Oncidium tigrinum (Fig. 10) has a large but simple lip, while in 

 Cypripedium the lip is curiously infolded into a slipper-like form, 

 presenting a wide contrast with the preceding. Frequently the 

 lip is partly divided into three lobes a large central one, and 

 two smaller ones at the side or by contraction it appears to be 

 composed of three distinct parts, the lower termed the hypo- 

 chilium, the middle the mesochilium, and the upper one the 

 epichilium, which are sometimes shortened in descriptions to 

 hypochil, &c. Several curious forms of lips are shown in Fig. 3. 

 Thus Prescottia colorans and Catasetum viride, as in several 

 other species, have the labellum shaped like hoods. Oncidium 

 raniferum has it formed like a frog, and in Ophrys muscifera, 

 O. apifera, with O. aranifera, the lip bears some resemblance to 

 the fly, a bee, and a spider respectively. 



Seores of equally strange formations could be named, but there 

 is another respect in which the lip of Orchids is remarkable, 

 namely, its irritability, which appears to be one of the many 

 contrivances to effect cross fertilisation. The genera Megac- 

 linium, Bolbophyllum, Pterostylis and Caleana yield several 

 examples of this phenomenon. Caleana nigrita has been thus 

 described: "The column is a boat-shaped box resembling a 

 lower lip, the labellum forms a lid that exactly fits it, and is 

 hinged on a claw, which reaches the middle of the column. 

 When the flower opens the labellum turns round and falls back, 

 so that the flower being inverted, it stands fairly over the column. 

 The moment a small insect touches its point, the labellum makes 

 a sudden revolution, brings the point to the bottom of the column, 

 passing the anther on its way, and thus makes prisoner any 

 insect which the box will hold. When it catches an insect it 

 remains shut while its prey continues to move about, but if no 

 capture is made, the lid soon recovers its position." The lip of 



