248 



PLANT LIFE. 



pollen spores sift out through the pore so formed (fig. 264) j 

 or (2) a crack begins at one point and extends lengthwise of 

 the sporangium, in which case the anther is said to open by- 

 slits (figs. 259, 260, 261) ; or (3) the break occurs along a 

 line considerably curved, and the flap (valve) thus loosened 

 curls up or lifts so as to allow the escape of the spores (fig. 

 265). All three methods are dependent upon some special 



Fig. 265. 



Fig. 264.— Anther and pollen of a Rhododendron. A, the anther, opening by pores at 

 the end and allowing the pollen to escape. Magnified 8 diam. A', pollen grains ad- 

 herent in fours (tetrads) as formed in the mother cells ; the tetrads are held together by 

 a sticky material which draws out into cobwebby threads as they are separated. Mag- 

 nified so diam. — After Kerner. 



Fig. 265' — A flower of cinnamon, halved. The calyx and stamens are raised on a cup 

 developed around the pistil. The anthers open by uplifted valves, one for each spo- 

 rangium, which here are arranged in two stories instead of in pairs side by side. Mag- 

 nified about 7 diam.— After Luerssen. 



structure of the wall of the sporangium at the lines of rup- 

 ture. 



349. Union. — The stamens are not infrequently united 

 with each other or with some of the neighboring leaves of 

 the flower. They may be united to each other by their fila- 



