LABORATORY PRACTICE 



5. Dichogamy. A more or less complete separation of the 



sexes is made in perfect flowers by the maturation of 

 the pollen and the stigmas at different times. It is 

 found both in wind- and in insect-pollinated flowers. 

 The effect is to render the flowers functionally im- 

 perfect although perfect morphologically ; in fact, to 

 render them more or less perfectly monoscious. Such 

 cases are very common, occurring in most perfect 

 flowers. There are two kinds of this method of 

 separating the sexes, or dichogamy, as it is called : 



(a) Proterogyny (or protogyny), where the stigma 



matures first ; and 



(b) Proterandry (or protandry), where the anthers 



open before the stigma is receptive (i.e. ma- 

 ture) . 



Dichogamy, I Prot gy nv > 

 y ' 1 Protandry. 



6. Examine a flower cluster of a species of Figwort 



(Scrophularia) or of the common Plantain, and 



notice : 



(a) That in the upper flowers the stigmas are pro- 

 truded while the anthers are still unopened. 



() In the lower flowers, the anthers are opening, 

 but the stigmas are withered. 



(<:) Is this protogyny or protandry? 



7. Examine the flower clusters of a Geranium or some 



kind of Mallow (Malva, Lavatera, Abutilon, or 



Hibiscus} and notice : 



(a) That in the upper flowers, the anthers are shed- 

 ding their pollen, but that the stigmas are not 

 opened, while 



() In the lower flowers, the anthers are empty and 

 the stigmas are open. 



