XXXIV 



MORPHOLOGY OF FLOWER 



467 



assumption of a petaloid form by the outer stamens, various 

 intermediate stages being present from the typical stamen, 

 through irregular leaves with anther-lobes at their distal ends, 

 to the ordinary broad white petal. 



We see, then, that a stamen is a leaf on the surface ot 

 which four microsporangia (B 1 , mi. spg) are developed : the 

 blade of the leaf is narrowed to form a mere stalk, while the 



FIG. 125.- A J -A 4 , transition from petal to stamen : mi. sbg, micro- 

 sporangia ; fl, filament ; an, anther. 



B 1 , transverse section of male sporophyll in the stage A 2 ; mr, mid- 

 rib of staminal leaf ; mi. spg, microsporangia. 



B 2 , transverse section of typical anther, showing connective (cor] with 

 vascular bundle or midrib (mr}, on the left two microsporangia (mi. 

 spg], and on the right the escape of the microspores (mi. sp} by dehis- 

 cence of the anther. 



microsporangia have become so closely aggregated as to 

 form a single four-lobed body, the anther (B 2 ). 



Similarly the carpel can be shown to conform to the leaf- 

 type. The flower of the cherry has a single flask-shaped 

 carpel, consisting of a rounded venter, with an expanded 

 stigma borne on the end of a stalk or style. But when the 

 cherry flower becomes double, the normal carpel is replaced 

 by a little green leaf, quite like a foliage-leaf, except that it 

 is permanently folded upon the midrib so as to bring the 

 two halves of its upper or dorsal surface almost into contact 



H H 2 



