DEVELOPMENT OF PLANTS 387 



those of the previous family, but the crowding on the receptacle 

 has resulted in the obliteration of one whorl of stamens. The 

 structure of the flowers often shows a series of variations that 

 adapt them to insect visitors and crossing - , as is well illustrated 

 in the iris (Fig. 289, B, C). The styles have a very unusual 

 form, resembling a leafy organ with the stigma on the upper side 

 of a small projecting shelf. Beneath each of these curving styles 

 is a stamen. The insect naturally alights upon the broad leaf 

 of the outer whorl of the perianth and the peculiar coloration of 

 this leaf probably directs him to the nectar secreted at the base 

 of the perianth. In reaching this food he crowds down into the 

 tube and rubs off the microspores upon his back. In leaving the 

 flower he cannot hit the stigma, but in visiting another flower it 

 can readily be seen that he will deposit some of the spores upon 

 the stigma situated upon the top of the shelf, thus effecting a 

 crossing. This order includes a large number of showy culti- 

 vated forms, as the iris, fleur-de-lis, crocus, gladiolus, friesia, 

 blue-eyed grass, etc. 



134. The Scitaminales. — This order is confined largely to the 

 tropics and includes such familiar plants as the banana, the trav- 

 eler's tree, ginger plant, canna, etc. It is mentioned here as fur- 

 nishing an interesting illustration of the variations that often 

 appear in epigynous flowers as a result of the crowding of the 

 organs upon the receptacle. Tendencies toward irregularity 

 appeared in the epigynous families of the Liliales, but in this 

 order these variations become very marked and make less abrupt 

 the transition to the next order. The flowers of the banana are 

 suggestive of the amaryllis family, though somewhat irregular. 

 All of the perianth leaves are united but one and only five per- 

 fect stamens are developed. These flowers are united into groups 

 in the axils of bracts that form large buds at the ends of the stem. 

 As the bud elongates, the basal or lower bract is first curved 

 back from the bud, thus exposing the flower cluster, and this 

 expansion goes on until all the flowers are exposed. The lowest 

 flowers in the inflorescence are imperfect, containing only pistils, 

 the central are perfect and the upper ones bear only stamens. 

 Only the ovaries of the lower flowers of the inflorescence develop, 



