1706 



A TEXTBOOK OF THEORETICAL BOTANY 



Fig. 1573- — Ai i\/<iliiihia clematitis. Flowering 



plant. 



in parts of England. The pollination mech- 

 anism of this herbaceous type is of special 

 interest (Fig. 1574). The flowers are long 

 and tubular, several being produced together 

 in the axil of a leaf. The flowers when 

 young are vertical and bright yellow in 

 colour. The perianth tube is produced 

 above into a flat lip, while below it is 

 swollen into a sort of bag. The slender 

 middle tube is lined with downwardly pro- 

 jecting stiff hairs. Many flies and gnats 

 find their way into the tube and cannot 

 escape because of these hairs. They appar- 

 ently fall in, for no nectar is secreted to 

 attract them. The gynoecium ripens first 

 and flies already covered with pollen are 

 almost certain to blunder against the style 

 in their attempt to escape. Later the anthers 



Fig. is74-—^ristolochia clematitis. dehisce and the flies become liberally dusted 

 Pollination. A, Female stage . , ,, ^.m 1 • 1 • 1 j 

 with receptive stigmas. B, Later With pollen. 1 he hairs now shrivcl and con- 

 stage with stigmas rolled up and tract, leaving the way open for the flies to 



anthers dehisced. The perianth ... , . , . . 



hairs have shrivelled up. escape while at the same time the perianth 



