DEVELOPMENT OF PLANTS 



457 



buckeye (Aesculus), etc. The flowers are more commonly small, 

 of a yellow-green color and variously grouped into inflorescences 

 (Fig. 318, A). We noticed in the rose order as the dominant 

 characteristic the tendency towards the development of the basal 

 region of the receptacle which was associated with the checking 

 of its apical growth. In the Sapindales a. similar shortening 

 of the axis without its basal growth leads to quite a different 

 series of variations. As a result of the crowding of the parts 

 of the flower upon the shortened receptacle, the distinguishing 



Fig. 318. A common form of the Sapindales: A, inflorescence of sugar 

 maple (Acer saccharum)—s, staminate flowers; p, pistillate flowers. B, 

 staminate (right-hand) and pistillate flower enlarged. C, section of a pis- 

 tillate flower, showing the two sterile stamens and nectar disc at base of fila- 

 ments. D, section of ovary, showing early development of the wings of the 

 fruit and the perpendicular ovules with micropyle pointing down. 



features of the order are seen in the reduction of the number 

 of the organs of the flower, a tendency towards the cyclic arrange- 

 ment of parts and an adhesion of the carpels. For example, 

 the sepals and petals are four to five in number, usually distinct 

 and the corolla may be entirely suppressed. There are t%\'0 

 whorls of stamens, five to eight in number, rarely ten, while 

 the pistils are reduced in number, ranging from two to more 

 commonly three or rarely five. Thus we see that the spiral 



