IO2 



NATURE OF 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 



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 o, 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. 



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

 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 

 that varies in different plants exposing the microspores to the 

 air (Fig. 75, B). The pistil or carpel is quite different in 

 character. At or near the top is a more or less modified part, 



