POLLEN. 39 



in which the cells present wavy or undulate walls. 

 In the petal (fig. 24), the walls are inflexed at tole- 

 rably regular distances, so as to give rise to the ap- 

 pearance of a row of teeth lining the cell. If the 

 strip of petal be folded, so as to exhibit the side view, 

 it will also be seen that the cells project outwards 

 from the surface to form a bluntish point or papilla, 

 or the petals are papillose as it is called ; and the 

 surface of the membrane around the papillae is finely 

 wrinkled, so as to present the appearance of very deli- 

 cate radiating lines or striae. Intermediate degrees 

 of this inflexion may be found in various flowers, 

 between the slight condition seen in fig. 13 and the 

 extreme state of fig. 24, as in the snapdragon (An- 

 tirrhinum mdjus). 



Anthers. The cavities of the anthers are lined 

 with fibro- cellular tissue, the fibres of which aid in 

 discharging the pollen ; this may be seen by dissect- 

 ing an anther of London pride (Saxifraga umbrosd], 

 or of a wallflower (Cheiran 'thus cheiri] in water. It 

 also exists in chickweed. 



Pollen. The pollen consists of minute grains called 

 the pollen-granules. They may be viewed either in 

 the dry state as opake objects, or when immersed in 

 water as transparent objects. As it is often difficult 

 to moisten them, they may be touched on the slide 

 with a little spirit, and then a drop of water added. 

 Their forms are very varied and curious, but they are 

 difficult of observation from their minute size. They 

 consist of one or more coloured cells, and these cells 

 are remarkable for their surfaces exhibiting spines, 

 networks, folds, and markings of various kinds. Thus 

 in the primrose the pollen- granules are cylindrical, 

 the surface being furrowed (PI. I. fig. 16) ; in the sun- 

 flower the granules are spherical, and covered with 

 tubercles surmounted by spines (fig. 17) ; in the 

 garden convolvulus the surface of the spherical gra- 

 nules is covered with an elegant network, in the 



E2 



