SPERMATOPHYTES: ATs^GIOSPERMS 3^5 



like small foliage leaves, and the inner set (corolla) becom- 

 ing more delicate in texture, larger, and generally brightly 

 colored (Fig. 71). 



2. From spiral to cyclic flowers. — In the simplest flowers 

 the sporophylls and floral leaves (if any) are distributed 

 about an elongated axis in a spiral, like a succession of 

 leaves. As this axis is elongated and capable of continued 

 growth, an indefinite number of each floral organ may ap- 

 pear. The spiral arrangement and indefinite numbers, 

 therefore, are regarded as primitive characters. 



In higher forms the axis becomes shorter, the spiral 

 closer, until finally the sets of organs seem to be thrown 

 into rosettes or cycles. These cycles may not appear in all 

 the organs of a flower, but finally, in the highest forms, all 

 the fioral organs are in definite cycles. All through this 

 evolution from the spiral to the cyclic arrangement there 

 is constantly appearing a tendency to " settle down " to 

 certain definite numbers, and when the complete cyclic 

 arrangement is finally established these numbers are estab- 

 lished, and they become characteristic of great groups. 

 For example, in the cyclic Monocotyledons there are nearly 

 always just three organs in each cycle, while in the cyclic 

 Dicotyledons the number five prevails. 



3. From hypogynous to epigynous floioers. — In the sim- 

 pler fiowers the sepals, petals, and stamens arise from be- 

 neath the ovary or ovaries (Fig. 72, i), and as in such cases 

 the ovary may be seen distinctly above the origin (inser- 

 tion) of the other parts, such a flower is often said to have 

 a "superior ovary," or to be hypogynous., meaning in effect 

 " under the ovary," referring to the fact that the insertion 

 of the other parts is under the ovary. 



There is a distinct tendency, however, for the insertion 

 of the outer parts to be carried higher up, until finally it is 

 above the ovary, and sepals, petals, and stamens seem to 

 arise from the top of the ovary (Fig. 72, «?), such a flower 

 being epigynous. In such cases the ovary does not appear 



