NECTAR AND ITS USES. 323 



Here the outer surface of the calyx is covered with small glands, the 

 secretion of which attracts bees to the flower ; but, strangely enough, 

 instead of alighting directly on the calyx and lapping up the nectar, 

 they settle on the wings and keel, whence they protrude their tongues 

 back into the flower and out between the separated bases of the petals, 

 thus indirectly reaching the nectar on the calyx. Despite their usual 

 intelligence, we are led to the conclusion that in this case the bees are 

 deceived, believing the nectar to be within the flower, as is the case in 

 so many of the Leguminpsoe, instead of on its exterior. But this decep- 

 tion, if deception it be, is of value to the plant, for in resting on the 

 wings and keel the bees depress these petals, bringing their breasts in 

 contact with stigma and pollen, and effecting the cross-fertilization of 

 different flowers, in their visits from plant to plant. 



Another example is afforded by the cucurbitaceous plant cultivated 

 in the South, under the name of bonnet-squash or dish-rag plant. Each 

 lobe of the calyx has on its outer side a varying number of glands, which 

 secrete nectar for some time before the flower opens during the period 

 of blooming, and for some time after fecundation has occurred. This 

 nectar is so greedily sought by ants of several species that numbers of 

 them are to be found at all times on every calyx which is in active secre- 

 tion, but they seldom enter the flower' apparently being prevented from 

 doing so by the large, spreading corolla. 



The common passion-flower or May-pop of the South (Passiflora 

 incarnata) affords a good illustration of nectar occurring on small, unmod- 

 ified bracts. At the base of every flower are found three or four small 

 bracts, each bearing two large nectar glands. Though the secretion of 

 these is not very plentiful, it is sufficiently so to attract swarms of ants, 

 which, as in the last case, do not enter the flowers, apparently finding 

 the spreading sepals and petals and the dense corona insurmountable 

 obstacles. 



In the tropical Marcgravia nepentlioldes (PI. Ill, Fig. C), Belt tells us 

 that "the flowers are disposed in a circle, hanging downwards, like an 

 inverted candelabrum. From the center of the circle of flowers is sus- 

 pended a number of pitcher-like vessels, which, when the flowers expand, 

 in February and March, are filled with a sweetish liquid. This liquid 

 attracts insects, and the insects numerous insectivorous birds. The 

 flowers are so disposed, with the stamens hanging downwards, that the 

 birds, to get at the pitchers, must brush against them, and thus convey 

 the pollen from one plant to another."* These pitcher-like vessels are 

 modified leaves or bracts, the nectar of each gland being secreted inside 

 a sort of pouch, and passing to the surface through two pores or ducts.t 



Good examples of nectar borne on bracts collected into an involucre 

 are afforded by some of the Euphorbias. Thus in E. (Poinsettia) pul- 



* Naturalist in Nicaragua, 1874, p. 128. 



tFor the structure of these glands see Wittmack, Botanisclie Zdtting, No. 35, Aug., 

 1879, s. 557. 



