SECT. xii. STAMENS AND POLLEN. 379 



fructifying organs consisting of stamens with their 

 anthers, and the pistil or pistils. 



The stamens are formed of very fine filaments, and 

 the anthers, when young and still enclosed in the unex- 

 panded flower, are full of a liquid which is afterwards 

 changed into a delicate homogeneous, cellular tissue. 

 Then the internal part of that tissue becomes divided 

 into two kinds of cells, one of which goes to form the walls 

 of two lateral and parallel chambers or loculi, separated 

 by a part more or less continuous with the filament. 

 The other kind of cells are developed into pollen grains 

 within the chambers. They gradually form a cylindrical 

 assemblage of mother cells. Within each of these, four 

 cells are ultimately formed, each containing a single 

 pollen cell. In all plants, except the aquatic, the pollen 

 cells are soon clothed by the deposition of one or more 

 layers of cells, which form the outer membrane, on which 

 are impressed figures or markings peculiar to each species 

 of plant, such as slits, points, papillae, sharply defined 

 circles, pores, &c. The colour of the external layer is 

 generally yellow, rarely green, blue, or red ; the thread is 

 usually white, except in the fuchsia and some others. 

 When the pollen is ripe the chambers dehisce to emit it. 

 The opening is usually a slit between the valves which 

 close the chambers. The length of the slit is variable, 

 and the form of the pollen grains is equally so ; they are 

 commonly ellipsoidal, and attenuated at the extremities ; 

 but in all cases they are beautiful microscopic objects. 



The contents of the pollen grains consist of a liquid 

 containing mucilaginous granules, which is in circu- 

 lation. The granules increase in number towards the 

 period of maturation, mingled with oil globules, and 

 frequently starch. The circulation of the fluid ceases 

 long before maturation in all cases, except the Zostera ; 

 but the granules of the contents exhibit an active mole- 

 cular motion often within the pollen cell, and always 



