204 THE REPRODUCTIVE ORGANS 



Scarlet Pimpernel, Stock, and Crocus. It is an effective 

 means of securing a crop of seeds if cross-pollination fails. 



2. Cross-pollination, where the pollen is carried to the 

 stigma of another flower on the same plant or to the stigma 

 of a flower on another plant of the same species. 



Devices which favour or necessitate cross-pollination are 

 very common, and seeds resulting from such a cross are 

 often more numerous and produce better and healthier 

 plants than when self-pollination occurs. 



The more important means of securing cross-pollination 

 are : 



i. Stamens and pistil occurring in different flowers (dicli- 

 nous : Gr. di = double, Mine = a bed). 



(a) Staminate and pistillate flowers on the same plant 

 (monoecious), e. g. Pine, Hazel, Oak, and Birch. 



(b) Staminate and pistillate flowers on separate plants 

 (dioecious), e. g. Willow, Poplar, Red Campion, Dog's 

 Mercury, Crowberry. 



2. Stamens and pistil occurring in the same flower 

 (hermaphrodite), but are not ripe at the same time (dicho- 

 gamous : Gr. dicha = in two parts), though the male and 

 female stages usually overlap, at which time self-pollination 

 may occur. 



(a) Stamens ripen and shed their pollen before the pistil 

 is ripe (proterandrous), e. g. Daisy, Dandelion, and other 

 Compositae ; Mallow, Wood Sorrel, Meadow Crane's-bill, 

 Chervil and other umbelliferous flowers. 



(b) Pistils ripen before the stamens (proterogynous), 

 e. g. Field Wood-rush and Plantains. 



3. Anthers and stigmas are so situated that the pollen 

 does not fall on to the stigma, e. g. Pansy, Buttercup (see 

 pp. 167-8). 



4. Different forms of flowers occur in the same species 

 (heteromorphic, Gr. hetero = different). 



(a) Long- and short-styled forms (dimorphic), e. g. 



