The Pollination Mechanism of Arctotis aspera. 219 
less than half a minute. It remains in the position assumed after 
the reaction until touched again. It has been observed, however, 
that when a style has been touched and has reacted in a given 
direction a longer time elapses before it will react in the opposite 
direction. Accurate time observations of these reactions would be 
interesting from a physiological point of view, but have no direct 
bearing on the present subject. 
After the first day of the male stage the style is withdrawn 
completely within the staminal tube, usually starting about 4 p.m. 
and retiring slowly. Sometimes very little pollen is scraped off as 
the style is retracted but more frequently a distinct ring of pollen 
is left adhering to the top of the staminal tube (Fig. 1, E). In the 
case of the F3 florets the style emerges the following morning 
slowly and in the female stage (Fig. 3). Then it is not sensitive to 
touch and has no pollen attached to the outside which is now 
comparatively smooth. The F2 and FI florets act similarly. One 
or two rows of florets grow up each night in regular succession 
until the whole of the disc florets have opened. In the female stage, 
however, the styles of the F2 florets are not exserted to the same 
extent as those of the F3 florets and those of the FI are exserted 
less than those of the F2 florets. The florets lying inside the FI 
row exsert irritable styles in the same way as the outer florets, but 
in these the style may emerge for two or even three successive days 
in the male stage and is retracted during the intervening nights. 
Little or no pollen is scraped off the first evening but on the second 
and third days all the pollen is removed from the style as it with¬ 
draws into the staminal tube. The ring of pollen is very distinct 
during the first twelve or eighteen hours lying around the top of 
the staminal tube, but gradually breaks up and a powdery mass is 
left around the top of the floret. The styles in these florets are not 
exserted again after the male stage is past. 
As a rule there is only one row of styles in the irritable phase 
each day but sometimes two rows mature more or less simultaneously, 
the inner row emerging later in the morning of the same day or the 
following morning at the same time as the styles of the outer row 
are exserted. 
The styles of the ray florets become gradually more and more 
exserted up to the time of fruiting, making their first appearance 
while the F2 florets are in the male stage. They are not retracted 
during the night nor are the styles of the F florets in the female 
stage. When the last disc florets are in the active stage the 
