1344 A TEXTBOOK OF THEORETICAL BOTANY 



style, arched over by the 

 bifid stigma. The flower 

 is devoid of nectar, but 

 on the floor of the spur 

 are a number of unicel- 

 lular capitate glands, the 

 heads of which contain a 

 juicy substance attractive 

 to flies. In the mouth of 

 the spur is a bunch of 

 bristles which project 

 upwards and backwards 

 into it. The remaining 

 opening is large enough 

 to allow a fly to climb 

 over the bristles into the 



-PinguicuJa alpina A, Flower in longitudinal gpur, but when it tries tO 



. B, Stamens with anthers partly concealed • i j • . 



lower lobe of stigma. (After Schroeter.) Withdraw it IS Opposed by 



Fig. 1253.- 

 section 

 bv the 



the points of the bristles. This 

 forces it to push upwards and 

 it then comes into contact with 

 the anthers and in this way 

 becomes dusted with pollen. 

 As it struggles outwards it 

 turns up the lower flap of the 

 stigma, preventing the pollen 

 from coming into contact with 

 the stigmatic surface, and thus 

 escapes. The flowers are 

 stongly protogynous so that if, 

 after visiting an older flower, 

 it enters a young one, it will, 

 as it crawls down to the spur, 

 touch the lower and larger flap 

 of the stigma and deposit pollen 

 upon it. 



[d] Explosive mechanism. 

 Crucianella stylosa is a member 

 of the Rubiaceae, with the 

 habit of a Galium and heads of 

 pink flowers (Fig. 1254). Its 

 honey scent attracts both Dip- 

 tera and Hymenoptera, but the 

 insects get a surprising wel- 

 come. The style elongates 



Fig. 1254. — Cnicianella stylosa. Inflorescence show- 

 ing styles and stigmas extruded. 



