MODES OF POLLINATION AND DISTRIBUTION OF SEXES 29 



A. All flowers are unisexual : Dicliny (Division of sexes). Only Allogamy 

 possible. 



1 . Male and female flowers on the same plant : Monoecism (Linnaeus) or 

 One-house plan. Geitonogamy and Xenogamy are possible. 



2. Male and female flowers on different plants : Dioecism (Linnaeus) or 

 Two-house plan. Only Xenogamy is possible. 



B. All flowers are hermaphrodite : Monocliny (Linnaeus) or Bi-sexuality. 



1. The stigmas and anthers of the same flower are not simultaneously mature : 

 Dichogamy (Sprengel). If this peculiarity is so well marked that the stigmas 

 have dried when the anthers spring up, or vice versa, only Cross-pollination is 

 possible. If it is not so well marked. Self-pollination is possible later on. Dichogamy 

 appears in two forms : — 



(a) The anthers are ripe before the stigmas have developed: proterandry 



(Delpino) or protandry (Hildebrand). 

 (3) The stigmas are ready to receive pollen before the anthers dehisce : 



proterogyny (Delpino)', protogyny (Hildebrand). 



2. The stigmas and anthers of a flower are simultaneously mature : Homogamy 

 (Sprengel). 



a. The flowers are open at the time of the maturity of stigma and anthers : 

 Chasmogamy (Axell). 

 a. Spontaneous self-pollination is impossible in consequence of the relative 



positions of stigma and anthers : Herkogamy (Axell). 

 |3. Spontaneous self-pollination is rendered possible by the relative positions 

 of stigma and anthers: 

 (a) All flowers are similarly constructed as regards length of style and 



stamens : Homomorphy or Homostyly (Hildebrand). 

 (0) On different plants there are flowers distinguished by a difi'erence in 

 length of stamens and style : Heteromorphy. 

 * The styles and also the stamens are of diff'erent lengths : Heterostyly 

 (Hildebrand). 

 + Two different forms of flowers occur : some with long styles and 

 short stamens, others with short styles and long stamens: Di- 

 morphism (or better, HeUrodislyly). 

 tt Three different forms of flowers occur : some with long styles and 

 medium and short stamens, others with medium styles and long 

 and short stamens, others with short styles and long and medium 

 stamens: Trimorphism (or better, Heterotristyly). 

 ** Only the stamens are of different lengths : Heteranthery. 

 b. The flowers are closed at the time of maturity of stigma and anthers: 

 Cleistogamy (Kuhn). 



1 Delpino distingnishes (i) Proterogynia brachybiostigmata, that is Proterogyny with short- 

 lived stigmas, if the stigmas fade before the anthers bnrst so that self-pollination is prevented, and 

 (a) Pr. macrobiostigmata (Pr. with persistent stigmas) when the stigmas remain capable of receivmg 

 pollen till the anthers are ripe, so that self-pollination is at least possible. 



