ESSENTIAL FLORAL LEAVES. 97 
The anther lobes present various shapes, linear, oval, kidney- 
shaped, &c., and they may possess tail-like appendages, as in 
heath. One lobe may be aborted, as in sage 
(fig. 46), while in mallow the anther produced 
by branching have also but one lobe, and are, 
so to speak, half-anthers. ‘The surface of the 
anther may be more or less hairy, as in dead 
nettle. When the pollen is ripe, the anthers 
open or dehisce to liberate it. Most commonly 
each lobe splits longitudinally, and the slit faces 
to the side, interior, or exterior, according as 
the anther is innate, introrse, or extrorse. In 
other cases, as potato and heath, a pore or minute 
fissure is formed at the tip of each lobe. In 
barberry the dehiscence is valvular, 7.e., part of 
the wall in each lobe becomes detached and turns 
up as a kind of flap, which remains united to ,,, 6 ee 
the tip of the anther. Sage. f. filament; 
Pollen is usually in the form of a fine sticky g._,ponneative 5 if 
or dry powder, composed of an Immense num- ds, Donte \ aces 
ber of minute pollen grains. Inheathandrho- ~ a 
dodendron several grains are united together, and in orchids the 
whole of the pollen in each lobe of the solitary anther is agglu- 
tinated into a club-shaped mass termed a polliniwm (fig. 47). 
Stamens sometimes occur in which the anthers are absent. 
They are then termed staminodia, and are often leaf-like. Com- 
pare the allied forms, mullein, pentastemon, snap- 
dragon, and foxglove (cf p. 94). These possess, 
respectively, five stamens, four stamens and a large 
staminode, four perfect and one aborted stamens, 
and four stamens. We are justified, therefore, in 
concluding that an odd fifth stamen has been sup- 
pressed or absolutely done away with in foxglove, 
especially as, so to speak, there is a “‘ vacant chair ”’ 
left by it. Similarly (cf p. 93), if we take the closely Fi. 47.—Pollinia 
related water-pimpernel and primrose, we shall find = * O°". 
that one has four perfect stamens superposed to the petals and four 
staminodes alternating with them, the other four stamens super- 
pose to the petals. Hence the conclusion is reached that a whorl 
of stamens has been suppressed in primrose. Observations like 
these, extended over a large number of cases, have led to the 
conclusion that two whorls are typical for the andreecium. 
Yellow is the most common colour for stamens, especially the 
anthers, but this is by no means an invariable rule. 
Structure.—The three systems of tissue can be recognized in 
G 
