DEVELOPMENT OF THE ANTHER 139 



way from petals tipped with a bit of anther, through stamens 

 with a broad petal-like filament, to regular stamens, as is shown 

 in Fig. 150, A, B, C, D. The same thing is shown in many double 

 roses. In completely double flowers the stamens and pistils are 

 transformed into petals by cultivation. In the flowers of the 

 cultivated double cherry the pistils occasionally take the form 

 of small leaves, and some roses turn wholly into green leaves. 



Summing up, then, we know that flowers are altered and 

 shortened branches, (1) because flower buds have, as regards 



BCD 



FIG. 150. Transitions from petals to stamens in white water lily 

 A, B, C, D, various steps between petal and stamen. After Brown 



position, the same kind of origin as leaf buds ; (2) because all 

 the intermediate steps are found between bracts on the one 

 hand and petals on the other. 



171. Development of the anther. If the development of an 

 anther is followed throughout, it will be found at an early stage 

 to contain, usually, four regions, where rapid cell division is 

 going on, which become organized into pollen sacs. These cavi- 

 ties (Fig. 151) are filled with pollen grains and finally merge into 

 two pollen chambers which, in the commonest type of anther, 

 split open lengthwise to allow the escape of the pollen. 



172. Relation of stamens and carpels to structures in the 

 lower plants. The exact significance of the stamens and car- 

 pels as organs of the plant body set apart for the purpose of 



