43 



petals. Two of the petals are narrow, united at the top, 

 and enclose the six stamens, three on each side. When a 

 bee {Bombus) hanging from the flower puts its proboscis 

 into one of the two channels which occur on the petals, it 

 presses the hood and stamens to one side, but the style, 

 which is stiff, remains in position and is rubbed by the bee's 

 body. A bee goes both to the right and left sides on each 

 visit. In this way it is certain to carry away some of the 

 pollen. 



Gorydalis cava- The flowers are borne in racemes. 

 Each flower has two small, scale-like sepals that soon fall off'. 

 The four petals occur in two pairs ; one being spurred . The 

 nectar is secreted in the lower end. The other petal serves 

 as a support for insects when in the act of obtaining nectar. 

 The inner petals enclose the stamens and stigma. This has 

 been called the hood. It is indented on both sides and when 

 touched the six diadelphous stamens and pistil are liberated. 

 Behrens says: "Previous to the opening of the flower the 

 pollen from the anthers is shed upon the stigma while it lies 

 in contact with them." Self-pollination would seem easy, 

 but if the flowers are enclosed by a gauze bag no seeds will 

 set. The insect on reaching the flower pushes its head be- 

 tween the hood and upper petal, the hood is pressed down- 

 wards and the pollen rubs against the lower surface of the 

 insect's body. The ho.)d returns to its normal position and 

 encloses the stamens and pistil. 



The Cruciferae show great uniformity so far 

 Cruclferae. 



as the structure of the flower is concerned 



but variability in the number and position of the nectar 



glands. The honey secreted by the glands remains on the 



gland or is found in spaces between them. They are visited 



