496 



BOTANY OF THE LIVING PLANT 



accessory formation, and only appears late, after the other parts have been 

 formed. From the inner surface of the perianth- tube, near to its base, arise 

 the six epiphyllous stamens. They are closely grouped round the central style, 

 whose stigma projects beyond them. Honey-secretion is provided by three 

 deep glands in the septa of the ovary, and it flows into the base of the tube. 

 The size of the flower allows entry to humble-bees, which, passing from flower 

 to flower, make cross-pollination probable. 



Narcissus poeticus, L., the Pheasant's Eye, is a species of similar construction, 

 but with white perianth, and a corona fringed with red. Its tube is, however, 

 narrow, and the anthers and stigma almost fill its opening. Thus it is inacces- 

 sible to bees ; but its white colour, heavy scent, and the length of the narrow 

 tube fit it for pollination by long-tongued, night-flying moths. These three 

 types of Amaryllids show how the'same floral structure may be modified as a 

 mechanism for pollination by different types of insects. 



Family : IRIDACEAE. Example : YELLOW FLAG. 



(5) Those Liliales which have inferior ovary and only three stamens, are 

 grouped as the Iridaceae, of which the native Yellow Flag (Iris pseudacorus, L.) 



FIG. 400. 



Iris pseudacorus, L. I. Complete flower. II. Same cut in median section. 

 III. Flower with perianth removed. IV. Single lobe of petaloid style, with stigmatic 

 lip. V. Floral diagram. 



serves as an example. It has a branched and strongly rooted perennial 

 stock (see Fig. 112, p. 164), and each branch ends in an annual foliage-shoot, 

 with sword-shaped leaves, sheathing at the base. The apex of certain shoots 

 extends upwards into the cylindrical flowering shoots, which bear their first 

 flower distally ; a second flower arises subsequently in the axil of a bract 

 below it, and others may follow, in sympodial arrangement. 



The large yellow flower is composed of the following parts (Fig. 400) : 

 Perianth, segments 3-3, gamophyllous at the base, superior ; the outer 

 series broad and recurved, the inner narrower, and erect. 



