: i66 Plant Life and Evolution 



ers occur, it is a question which of these two types 

 is the older. 



The petaloideous monocotyledons constitute the 

 second category, in most of which the floral envel- 

 opes are conspicuous, and these include some of the 

 most beautiful and highly specialized of all flowers. 

 The simplest types are seen in the lilies, e.g., tu- 

 lip, hyacinth, trillium, etc. They have the char- 

 acteristic three-fold arrangement of the floral or- 

 gans with all the parts separate except the three 

 united carpels; but the leaves of the floral envelope 

 may be more or less united, as in the hyacinth or 

 lily-of-the-valley. This appears to be the central 

 type from which have radiated several lines of de- 

 velopment, resulting in flowers differing a good deal 

 from the primitive lily type. 



The deviations from the primitive type are two- 

 fold. First there is a reduction in the number of 

 stamens, and second, a more or less complete fusion 

 of certain parts of the flower. The simplest case is 

 seen in the Amaryllis family, of which the narcissus 

 and snowdrop are common examples. In these flow- 

 ers the base of the floral envelope, and probably to 

 some extent the floral axis, are fused with the lower 

 parts of the carpels, so that there is formed an " in- 

 ferior " ovary. Otherwise, the flowers are like those 

 of the lily. In all of the higher types of monocoty- 

 ledonous flowers there is an inferior ovary. In the 

 Iris family there is a reduction of stamens to three, 

 and a strong tendency to replace the radial symmetry 



