6io 



BOTANY OF THE LIVING PLANT 



agency than most of the Iridaceae. Many of them, such as Ixia, or Sisy- 

 rinchium, have flowers not unlike the Snowdrop, but with only three stamens. 

 Gladiolus has the same, but it is slightly zygomorphic. (6) Crocus has a 

 tubular perianth greatly elongated, so that while the ovary is seated just above 

 the underground corm, the perianth, stamens, and stigmas are above ground. 

 But Iris is the most specialised of them all. Its peculiar features are that the 

 three stamens, which open outwards, are enclosed each between one of the 

 broad outer perianth-segments and one of the three broadly petaloid styles 

 (Fig. 458, in, iv.). The tip of each style is two-lobed, and bears a project- 

 ing lip on its lower and outer surface. This is the stigma. The fact that 

 the styles are opposite the stamens, and these opposite the outer perianth- 

 segments, shows that it is the inner stamens that are wanting (v.). Honey is 



Fig. 458. 

 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. 



secreted by the inner surface of the perianth-tube, and collects round the base 

 of the styles. Each third of the flower may be pollinated independently by 

 humble-bees, which force their way between the perianth-segment and its 

 opposing style. On entering, if they bring pollen, it is swept off on the project- 

 ing stigmatic lip ; the stamen then deposits a fresh supply of pollen upon his 

 body, which he carries away. Self-pollination is mechanically impossible ; but 

 cross-pollination results with high probability from a succession of visits, either 

 to other thirds of the same flower or to different flowers. In many forms of 

 Iris the parts fit so exactly as to exclude small and weak insects that would 

 not effect pollination, but this exclusion is less perfect in others. Iris may 

 be held to show a culmination of pollination-mechanism as seen in the Liliales. 

 The Iridaceae are widely spread; but are specially frequent in the Cape 

 Flora. They include plants grown for their showy flowers (Crocus, Iris, 

 Gladiolus, Ixia). The dried rhizomes of species of Iris give the "Orris-root," 

 and the stigmas of Crocus sativus are the source of Saffron. 



