198 



PLANT STRUCTURES 



If a young anther be sectioned transversely four sporan- 

 gia will be found imbedded beneath the epidermis, a pair 

 on each side of the axis (Figs. 166, 167). When they reach 

 maturity, the paired sporangia on each side usually merge to- 

 gether, forming two spore-containing cavities (Fig. 167, B). 

 These are generally called " pollen-sacs," and each anther is 

 said to consist of two pollen-sacs, although each sac is made 

 up of two merged sporangia, and is not the equivalent of the 

 pollen-sac in Gymnosperms, which is a single sporangium. 



FIG. 167a. Various forms of stamens : A, from Solannm, showing dehiscence by 

 terminal pores; B, from Arbutus, showing anthers with terminal pores and 

 "horns"; C, from Herberts; Z>, from Atherosperma, showing dehiscence by 

 uplifted valves; E, from Aquilegia, showing longitudinal dehiscence ; F, from 

 Popowia. showing pollen-sacs near the middle of the stamen. After ENGLER 

 and PRANTL. 



