300 



ANTS. 



the nectaries have no other function in the life of the plant and cannot 

 he regarded as having arisen for some other function.'-' Neither of 

 these propositions has been established, although there is a little evi- 

 dence to show that the ants actually protect certain plants whose nec- 

 taries they are in the habit of visiting. But Schimper, who studied 

 this subject in I'.razil, admits that plants with extrafloral nectario 

 differ greatly in the extent to which they are visited by ants, and 1 have 

 reached a similar conclusion from observing species of Cassia, Stil- 

 linyia, Kicinus, Ailanthns and Populus. Schimper endeavored to 

 ascertain whether the extrafloral nectaries had any such function as 

 that attributed to them by Johow and Bonnier. He extirpated all the 

 nectaries of Cassia, and finding no visible changes in the well-being of 

 the plant, concluded that the organs have little importance in metabo- 

 lism and that their main function is to attract ants. This does not 

 follow from the experiment, however, for it is quite possible that with 

 extirpation of the organs under discussion their function might be 

 transferred to other parts of the plant. 



3. Food-bodies. These structures are known to occur in onlv a few 



plants peculiar to the American 

 tropics. ' In Cccropia and Poronma 

 they are called " Miillerian bodies," 

 and are yellow or red, elliptical cor- 

 puscles about the size of a millet 

 seed. They are found embedded 

 in a dense mat of hairs forming 

 a large cushion, or " trichilium " at 

 the base of the leaf-petiole. In 

 Cecropia these bodies, which 

 Schimper found to contain oily and 

 albuminous substances, are easily 

 detached and are carried away and 

 eaten by the ants. Whether this 

 is also the case in Porouma has not 

 been ascertained. Acacia sphicro- 

 ccphala possesses similar corpuscles. 



known as " Beltian bodies," but these are borne singly on the tips of 



the leaflets (Fig. 178, C). 



4. Bead-glands (" Perldriisen "). These are modified trichomes or 

 elevations, which sometimes appear as transparent bead-like bodies, 

 scattered in great numbers over the surfaces of green plants. Accord- 

 ing to Rettig (1904), they are characteristic of certain Yitaceae, Piper- 

 acese, Melastomaceae and Urticaceae, rarer in Moracere, Bigoniacese 



05-- - 



FIG. 170. Base of leaf with as- 

 cidia, of Tococa lancifolia. ( Escherich, 

 after Schumann.) a, Lower; b, upper 

 surface of leaf ; xx, openings of ascidia. 



