154 



ELEMENTS OF BOTANY. 



at first like an ordinary leaf and finally becomes folded in. 

 What really occurs is this : the flower-bud, as soon as it has 

 developed far enough to show the first rudiments of the 

 essential organs, contains them in the form of minute knobs. 

 These are developed from the tissues of the plant in the 

 same manner as are the knobs in a leaf-bud, which afterwards 

 become leaves ; but as growth and development progress in 

 the flower-bud, its contents soon show themselves to be sta- 

 mens and pistils (if the flower is a perfect one). The united 



leaf margins near the tip 

 would form the stigma, and 

 the placenta would corre- 

 spond to the same margins, 

 rolled slightly inwards, ex- 

 tending along the inside of 

 the inflated leaf pouch. 

 Place several such folded 

 leaves upright about a com- 

 mon center, and their cross- 

 section would be much like 

 that of B in Tig. 132. Evi- 

 dence that carpels are really 

 formed in this way may be 

 gained from the study of 

 such fruits as that of the 

 monkshood (Fig. 171), in 

 which the ripe carpels may be seen to unfold into a shape 

 much more leaf -like than that which they had while the pistil 

 was maturing. 



189. Tli6 Anther and its Contents. — Some of the shapes of 

 the anthers may be learned from Figs. 116, 129, 136, 138 and 

 155.^ The shape of the anther and the way in which it opens 

 depend largely upon the way in which the pollen is to be dis- 



I II in 



Fig. 138. — Modes of DiBoharging Pollen. 



I, by longitudinal slits in the anther-cells 

 (pin^); II, by uplifted valves (barberry); 

 III, by a pore at the top of each anther- 

 lobe (rhododendron). 



^ See Kemer and Oliver, vol. II, pp. 86-95. 



