268 BOTANY. 
541. In the Composite (Fig. 146) the five anthers are 
united into a ring or tube around the style. The pollen 
escapes from the inner side of the anthers into the anther- 
tube, and at this time the immature style is short. As the 
latter grows it pushes up through the anther-ring, carrying 
the mass of pollen with it. Insects visiting the flowers for 
nectar at this stage rub off the little piles of pollen from 
the top of the stamen-tubes, and coming in contact after- 
wards with the expanded stigmas of other flowers, some of 
the pollen is left upon them. 
542. After the pollen is set free the style elongates still 
more, and finally the two lobes of the stigma open out and. 
are ready for pollination. This development takes place 
beginning at the outer rows of flowers in each flower-head 
and proceeds towards the centre. Thus at any time in 
any blooming flower-head, as of the Sunflower, there may 
be seen a ring of pollen-bearing flowers and outside of it 
aring of flowers with expanded stigmas. In some Com- 
posites, in addition to these structural peculiarities, the 
stamens are sensitive, and when touched will suddenly 
contract, drawing the anther-tube down and ejecting pol- 
len. This may easily be seen by passing the finger quickly 
across the top of a thistle-head when in full bloom. 
543. The foregoing must serve to direct the student to 
the careful observation of the flowers of Dicotyledons. 
He should remember Lubbock’s remark that “ it is probable 
that all flowers which have an irregular corolla are polli- 
nated by insects,” and to this he may well add that it is 
equally probable that all tubular flowers are likewise polli- 
nated by insects. 
544, Among the interesting things to which attention 
has been directed during the past few years is that of the 
