ECOLOGY OF FLOWERS; POLLINATION 175 
Many flowers which appear to be designed to secure 
self-pollination are almost or quite incapable of it. Fre- 
quently the pollen from another plant of the same species 
prevails over that which the flower may shed on its own 
pistil, so that when both kinds are placed on the stigma 
together it is the foreign pollen which fertilizes. 
209. Dichogamy ; Movements of Stamens. — If the sta- 
mens mature at a different time from the pistils, self- 
pollination is as effectually 
prevented as though the 
plant were dicecious. This 
unequal maturing, or di- 
chogamy, occurs in many 
kinds of flowers. In some, 
the figwort and the com- 
mon plantain for example, 
the pistil develops before 
the stamens, but usually 
the reverse is the case. The 
Clerodendron,' a tropical 
African flower (Fig. 131), 
illustrates in a most strik- 
ing way the development 
of stamens before the pistil. 
Besides the slow move- 
ments which the stamens 
and pistil make in such 
Fig. 131. Flower of Clerodendron in 
Two Stages. 
In A (earlier stage) the stamens are ma- 
ture, while the pistil is still undevel- 
oped and bent to one side. In B (later 
stage) the stamens have withered and 
the stigmas have separated, ready for 
the reception of pollen. 
cases as that of the Clerodendron, the parts of the flower 
often, as in the barberry and Kalmia, admit of extensive 
and rather quick movements to assist the insect visitor to 
become dusted or smeared with pollen. 
1C. Thompsoniz. 
