Ii6 



NATURE OF THE SPOROPHYLLS 



sporophylls are the important organs of the flower. The calyx 

 and corolla may be lacking but no seed can be formed without 

 the sporophylls. 



51. The Structure of the Sporophylls. — Let us examine the 

 structure of these organs and see how they co-operate in the 

 formation of the seed. The stamens consist of a lobed sack or 

 anther which is usually supported upon a stalk or filament (Fig. 



1^ 



Fig. 74. Flower of the stonecrop, Sedum: A, bud stage of flower — ca, 

 calyx showing three sepals. B, open flower — p, petals of corolla; s, stamens; 

 c, pistils or carpels. C, stamen, consisting of a four-lobed anther supported 

 on delicate stalk or filament. D, pistil or carpel — 0, ovary; s, style which 

 terminates in a small knob or stigma. E, longitudinal section of ovary showing 

 row of ovules attached to wall of ovary. F, cross-section of ovary, ovules in 

 two rows. 



74, C). If a young anther is cut across four cavities, contain- 

 ing minute or dust-like grains, the microspores, will be seen 

 (Fig. 75, A). The microspores, also called pollen spores or 

 grains, are minute cells, provided with a cell wall often variously 

 sculptured and contain a nucleus and protoplasm like an ordinary 

 cell (Fig. 79). At maturity the anthers break open in a manner 



