320 



THE CROSSING OF FLOWERS. 



contain but few florets; those of Eupatoriwm cannabinum have five, which open one 

 after another in the course of 5-8 days. Younger and older flowers are therefore 

 always close together. The styles are rather diflferent from those of other Composites, 

 being divided almost half-way down into two long threadlike branches which 

 bear the stigmatic tissue only on their lower portions. The rest of the branch is 

 thickly studded with short bristles, the aforesaid sweeping hairs. The styles are 

 parallel and folded together as long as they are inclosed in the anther-tube (see 

 fig. 294 ^), and they remain closed for some time after they have elongated and 



Fig. 294. — Geitonogamy with adherent pollen. 



1 Crossing of the stylar branches of neighbouring florets in the capitulum of Eupatorium cannabinum. 2 Longitudinal section 

 through the upper part of a floret of Eupatorium; the two stylar branches are parallel and- inclosed by the anther-tube, 

 which is again surroimded by the corolla-tube. 3 Umbel of Chcerophyllum aromaticum; the truly hermaphrodite flowers 

 are open, the pseudo-hermaphrodite male flowers are still closed. •* The same umbel;, the true hermaphrodite flowers 

 ha"e lost their pollen; the male flowers are now open, and their anthers drop pollen on the stigmas of the hermaphrodite 

 flowers. All the figures somewhat enlarged. 



pushed their way above the anthers. During the elongation the sweeping hairs 

 brush the pollen from the anther-tube, and it then adheres in abundance to the 

 outer side of each style-branch. This condition, however, does not continue for long. 

 The stylar branches soon diverge at an angle of 40-50°. The branches of adjacent 

 styles now cross one another like rapiers, and when the pollen is detached from the 

 sweeping hairs it falls on to the mature stigmatic tissue. The closed pollen-covered 

 stylar branches, as they emerge from the anther-tube, come in contact with the 

 divergent branches of older neighbouring florets, and thus the pollen is transferred 

 to the stigmatic tissue of the latter. 



