177 
Before the flower opens the style branches are closed within 
the flower. The lines of stigmatic papillz are closed in against 
each other on the inner face of the style branches and thus re- 
main unexposed until after the flower opens and the branches 
separate. 
When the flower opens the style pushes up through the anther 
tube and the brush hairs brush out and collect the pollen as the 
anthers dehisce. 
The pollen thus held by the brush hairs is usuaily removed by 
insects before the stigmatic papilla are exposed. Self-pollination 
is therefore not likely to occur. As the style grows, the branches 
separate, often curving far back, and the stigmatic papillz are in a 
position to be readily pollinated by insects. By this mechanism 
cross-pollination of the Composite seems almost certain, though 
self-pollination does occur. 
In Xanthium, which is anemophilous, the brush hairs are not 
needed, and consequently they are more or less abortive. 
In the female flowers the style is always two-branched, but 
brush hairs are absent, as they would be useless. The stigmatic 
papilla cover the entire inner face of the branches or are arranged 
in two lines. Some exceptions occur, however, as in /zu/a* where 
the style of the pistillate ray flowers is like that of the her- 
maphrodite flowers. 
In male flowers the style is either entire or two- irdeto 
sometimes both forms occurring in the same genus. The pistil 
being sterile it has no function to perform except that of remov- 
ing the pollen from the anther tube, and consequently we find 
brush hairs but no stigmatic papillz. 
Cassini®, Lessing’®, De Candolle", and Lindley”, in their classi- 
fications seem to have noticed only the variations in the shape of 
the branches, while the differences in arrangement, size, shape, 
etc., of the brush hairs and the stigmatic papilla was unnoticed. 
Le Maout and Decaisne“, Bentham™ and Gray” all notice the 
brush hairs and stigmatic papillz to some extent, the latter using 
them for distinct tribal characters. 
8 Lubbock :—British Wild Flowers in Relation to Insects, p. 115. 
9L.c. Lc. Lc, % Flora Medica, p. 450. 
13 Descriptive Botany, p. 497. 
41 Gy ps 340. 95 dnc, p. 40. 
