LEGUMINOSAE 



265 



until the upper edges of the carinal petals are caused to separate. Each ala 

 possesses a fold which interlocks with an acutely angular projection on the upper 

 margin of the corresponding half of the carina. It therefore follows that when 

 a bee settles on the flower, resting with its limbs on the alae, and thrusting its 

 head under the vexillum, the alar folds slip down the column formed by the 

 filaments and the pistil, and at the same time the carina splits open above from 

 base to tip. When the splitting has extended as far as the end of the style, the 

 stretched parts suddenly separate, the carina and alae moving down, the style 

 with its superimposed pollen springing up. The stigma thus first touches the ventral 

 surface of the bee, and if this has previously visited another flower of the same 

 species it gets pollinated. Immediately afterwards the pollen is pressed against the 

 under-side of the visitor. If cross-pollination is not effected, self-pollination is 



/^ 



Fig. 83. Genista ttnc/oria, L. (after Herm. Muller). (i) The stamens with style and stigma; 

 taken from a bud. (3) Position of the parts enclosed in the carina in a flower not yet visited by insects. 

 (3)^Right ala, seen from within. (4) Exploded flower. (5) Unexploded flower, after removal of calyx 

 and \exillum ; seen from above. (6) The same, after the carina has been split open almost to tlie tip by 

 pressure from above. (7) Unexploded flower, after removal of vexillum and alae; seen from above 



(8) Anterior part of a flower split open and about to explode ; seen from above (enlarged to twice the 

 scale of the other Ggures). a, stamens with style and stigma ; d, the four outer stamens that have 

 remained short (2, 4, 8, 10 in Fig. i) ; c, the five inner stamens (i, 3, 5, 7, q) ; rf, the outer stamen (6) that lies 

 under tlie style ; c, tip of the style ; f, stigma ; ^, pollen ; /;, lateral projections of the carina, with which 

 corresponding alar folds (A') interlock. ; A/, that part of the upper margin of the carina which is split before 

 explosion; m, alae; n, carina. 



brought about by the insect as it backs out of the flower. Explosion has not been 

 observed to occur without the appHcation of external pressure. 



Visitors. — According to Hermann Muller, the visitors are chiefly pollen- 

 collecting bees, which sometimes also vainly seek for nectar. All of them, even 

 the nectar-seeking males, bring about explosion, and effect pollination in the way 

 already described. Among useless visitors are wasps, Conopidae, Syrphidae, Lepi- 

 doptera, and destructive beetles which gnaw the flowers (Cryptocephalus). 



