SPERMATOPHYTES : ANGIOSPERMS 
361 
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. 320, 321). When they reach 
maturity, the paired sporangia on each side usually merge to- 
gether, forming two spore-containing cavities (Fig. 321, 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. 
D 
FIG. 322. Various forms of stamens : A, from Solanum, showing dehiscence by 
terminal pores; B, from Arbutus, showing anthers with terminal pores and 
"horns"; C, from Herberts; D, 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 ENGLEB 
and PRANTL. 
