Chap. IX. CONCLUDING EEMAEKS. 289 



superfluity owing to the many special contriTances for 

 its safe transportal from plant to plant, and for placing 

 it securely on the stigma. Thus we can understand 

 why the Orchideae are more highly endowed in their 

 mechanism for cross-fertilisation, than are most other 

 plants. 



In my work on the "Effects of Cross and Self 

 Fertilisation in the Vegetable Kingdom," I have shown 

 that when flowers are cross-fertilised they generally 

 receive pollen from a distinct plant' and not that from 

 another flower on the same plant ; a cross of this latter 

 kind doing little or no good. I have further shown 

 that the benefits derived from a cross between two 

 plants depends* altogether on their differing some- 

 what in constitution ; and there is much evidence that 

 each individual seedling possesses its own peculiar 

 constitution. The crossing of distinct plants of the 

 same species is favoured or determined in various 

 ways, as described in the above work, but chiefly 

 by the prepotent action of pollen from another 

 plant over that from the same flower. Now with the 

 Orchidese it is highly probable that such prepotency 

 prevails, for we know from the valuable observa- 

 tions of Mr. Scott and Fritz Muller,* that with several 

 Orchids pollen from their own flower is quite im- 

 potent, and is even in some cases poisonous to the 

 stigma. Besides this prepotency, the Orchidese pre- 

 sent various special contrivances — such as the poUinia 

 not assuming a proper position for striking the stigma 

 until some time has elapsed after their removal from 

 the anthers — the slow curving forwards and then back- 

 wards of the rostellum in Listera and Neottia — the 



' A full abstract of these ob- Domestication,' oh. xvii. 2nil edit, 

 servations is given in my * Varia- vol. ii. p. 114. 

 tlon of Animals and Plants under 



