NECTAK AND ITS USES. 329 



produced in front of its mouth in the form of a fish or swallow tail. As 

 in the last case, the edge of the border of the wing, the mouth, and the 

 blade or fish-tail appendage are provided with a secretion of nectar, as 

 is also the inside of its arched hood ; so that insects are attracted as be- 

 fore by the sweets, only to meet their death on entering the tube. The 

 nectar leading from the ground appears designed to attract creeping 

 insects, such as the ants, which form a large part of the prey of Sarra- 

 cenias, while the swallow-tail appendage appears to be for the purpose 

 of attracting flying insects.* 



Like the preceding, the climbing Indian pitcher-plants (Nepenthes) 

 secrete nectar about the mouths and on the lids of their cups, and for 

 the same purpose, for they, too, are insectivorous, and, indeed, more 

 truly so than either of the genera previously mentioned, inasmuch as 

 their secretion has been shown to be a true digestive fluid, while that 

 of the others is scarcely demonstrated as yet to be more than a liquid 

 in which maceration may go on. 



When the foregoing examples are considered, it appears at once that 

 all nectar may be divided into two classes, according as its relations to 

 the secreting plant are direct or indirect, according as it merely relieves 

 the plant of a waste or injurious substance, or serves to establish definite 

 relations between it and other living beings. Furthermore, the first 

 class is entirely excretory, and is produced either by the unmodified leaf 

 tissues or by specialized glands ; the second class is never excretory, 

 and may be subdivided into two groups as has been done by Delpino 

 the first aiding in reproduction, and being either intra or extra floral ; 

 the second taking no direct part in reproduction, being always extra- 

 floral, and serving indirectly either for the protection of some part of 

 the plant or for its nutrition by attracting animals which, in the one 

 instance, serve as a body-guard to the tender foliage and flowers, and 

 in the other are killed, their remains undergoing decomposition or even 

 digestion in the leaf cavities of the plant, and serving in either case as 

 food for it. This arrangement may be expressed in tabular form as 

 below : 



Directly useful .... Excretory 5 From the surface - 



< From glands. 



f Borne on Sepals. 

 I Borne on Petals. 



{Floral < Borne on Stamens. 

 Borne on Pistils. 

 iBorneonKeceptacle. 

 If Borne on Calyx. 

 Estrafloral <J Borne on Bracts. 



Indirect ly useful . . </ ^ Borne on frvoliicre. 



f To flowers. 



["Protective <( To fruit. 



I Non-reproductive. <| (^ To foliage. 



^ Nutritive By securing material for 



absorption by leaves. 



* See Canby, Proc. Am. As. Adv. Sc., xxiii, 1874, Nat. Hist., p. 64. 



