278 BRITISH FLOWERING PLANTS chap. 



fly, the weight of which presses down the lower Hp, 

 and thus opens the way to the honey. As in Antir- 

 rhinum the pistils and stamens lie close underneath the 

 upper lip. The pistil consists of two lobes — an upper 

 one, quite short and pointed ; and a lower one, which is 

 longer, spathulate, and bears the stigma on its upper 

 surface (Fig. 175). The stigma projects beyond the 

 anthers, so that it is first touched by any entering 

 insect. The anthers open downwards, so that the 

 head of the insect necessarily touches them and takes 

 up a fresh supply of pollen. The stigmatic surface, as 

 already mentioned, is on the upper side of the stigma, 

 and lies, therefore, against the upper lip of the corolla. 



Fig. 178. — Ulricularia vulgaris. Mouth of bladder, seen sideways, a, antenna ; 

 b, strengthened margin of fore- court ; c, flap. 



When the flower opens, however, it turns downwards 

 (Fig. 175) so as to touch the head of any insect visitor. 

 It is, moreover, sensitive, and as soon as it is touched it 

 rises again, and resumes its original position, so that the 

 retreating insect cannot dust it with any of its own 

 pollen. The edge of the stigma is furnished with a row 

 of hairs, which, according to Heinsius,^ serve to brush 

 the pollen from the head of the visitor. The pollen 

 grains lend themselves to this, being provided with 

 several longitudinal ridges. The visitors appear to be 

 especially flies belonging to the family Syrphidse. 



The flowers of U. minor and U. intermedia are formed 

 on the same general plan. 



In autumn most of the plant decays away, but the 



' Bot. Jaarb. iv. (1892). 



