LEGUMINOSAE 261 



4. Brush arrangement. A brush of hairs on the style sweeps the pollen out 

 from the tip of the carina. Here again repeated insect-visits are usually necessary 

 for pollination. 



(a) The tip of the style is straight : Lathyrus, Pisum, Vicia, Lens, Robinia. 



(b) The tip of the style is helicoid : Phaseolus. 



Papilionaceae possessing the brush arrangement are divided by Taubert (in 

 Engler and Prantl, 'D. nat. Pflanzenfam.,' Ill, 3, p. 92) into two subdivisions, 

 according as the sweeping apparatus acts exactly in the median plane of the flower 

 or not. In the former case the pollen is deposited on the ventral surface of the 

 visitor (' pollinazione sternotriba,' Delpino), e. g. in Vicia Cracca, V. sepium, V. Faba, 

 and also in Pisum sativum, which shows a combination of the pump and brush 

 arrangements. In the second case the brush emerges laterally and obliquely, not 

 in the median plane of the flower, so that the pollen can only be deposited on 

 the right or left side of the body of the visitor (' pollinazione pleurotriba,' Delpino). 

 An indication of a unilateral mechanism of the kind occurs in some species 

 of Lathyrus (L. sylvestris, L. 

 grandiflorus), while other species 

 of the same genus (e.g. L. 

 pratensis) have a median polli- 

 nating apparatus. The asym- 

 metry is more marked in species 

 of Phaseolus (P. vulgaris, P. 

 multiflorus), in which it is con- 

 ditioned by the helicoid spiral 



Of the tip Of the Style. In P. FlQ gl Af>igs tuberosa ^ Moench (after Taubert and Loew). 



Caracalla this COiling Of the A. Flower seen from the side after removal of half the calyx, half 



. . , the vexillum, and the right ala (X3). B. Sexual apparatus after 



Style IS mOSt pronounced, as removal of the corolla ; the stamens project on the right side and 



there are 4-5 turns in the the style on the left (x 4 ). 

 spiral. 



Apios tuberosa presents a transition to flower mechanisms of other kind, par- 

 ticularly characteristic of extra-European species. Here, according to Loew (Flora, 

 Marburg, lxxiv, 1891), the sickle-shaped tip of the carina is held fast in a cap- 

 shaped protuberance of the vexillum in such a way as to render impossible the 

 movements which usually take place in papilionaceous flowers, so that cross- 

 pollination has to be secured in another way (see Fig. 81). 



The species of Erythrina exhibit still another modification in the construction 

 of the flower. In E. Crista-galli, according to Hildebrand (Bot. Ztg., Leipzig, xxviii, 

 1870), the flower is so twisted that the pollinating apparatus is upside down, while 

 at the same time the alae and carina are much reduced. The latter forms a stiff, 

 immobile sheath, which surrounds the markedly projecting sexual organs above, 

 and expands below into a nectar-receptacle. Delpino supposed that species of 

 Trochilus and Nectarinia acted as pollinators. This supposition has been confirmed 

 by the direct observations of Scott-Elliot, who saw species of Nectarinia on E. caffra 

 Thunb. He further states that E. Indica Lam. and Sutherlandia frutescens R. Br. 

 are also ornithophilous. The alae and carina are entirely suppressed in Amorpha 



