POLLINATION AND FERTILISATION 221 



flowers have no scent ; (iii) the flowers produce great quantities of 



pollen which is dry ; (iv) the anthers are versatile and hang out of the 



flower ; (v) the stigmas are very large. 



Self-Pollinated Plants produce flowers which may be 



(a) Pollinated by the wind blowing the pollen from the anthers to the 



stigma of the same flower. 



(6) Pollinated by insects creeping over the flower and distributing the 



pollen from the anthers to the stigma of the same flower. 



(c) Pollinated by the stigma coming in contact with the anther of the 

 same flower. 



(d) Pollinated by the flower never opening cleistogamic flowers. 

 Fertilisation is the union of the generative nucleus of the pollen grain 



with the oosphere in the ovule. 



The Embryo Develops from the oospore by division. 



The Results of Fertilisation are 



(i) The oosphere changes into the oospore. 



(11) The oospore changes into the embryo. 



(iii) The embryo-sac is filled with a tissue the endosperm, 

 (iv) The ovule is converted into a seed, 

 (v) The ovary is converted into a fruit. 



QUESTIONS ON CHAPTER XVI. 



1 i ) Explain, giving examples, the meaning of the following terms- 

 dioecious, monoecious, diclinous, hermaphrodite, complete. (1897.) 



(2) What is meant by self-fertilisation and by cross-fertilisation? 

 Mention any plants in which the wind is the agent in pollination. ( 1891. ) 



(3) Describe the structure of the flower of any British Orchid, and 

 explain how pollination takes place. (1890.) 



(4) Mention three different flowers which are not pollinated by 

 insects, and explain in what respects they differ from flowers which are 

 so pollinated. State the means by which the pollination of these three 

 flowers is effected. (1894.) 



(5) Explain the way in which insects are of use to flowers, and the 

 means by which flowers attract them. 



(6) In what important respects do wind-fertilised flowers differ from 

 insect-fertilised flowers? Give examples of both. (1898.) 



(7) Explain briefly the biological significance of (a) brightly coloured, 

 and (b) irregular flowers, as compared with (c) inconspicuous and (d) 

 regular flowers. Give examples. 



(8) What is the use of the spurs formed from floral leaves ? Give 

 examples. 



(9) What is meant by heterostyled plants? Give examples. 



(10) Mention plants which produce cleistogamic flowers, and explain 

 of what use they are to the plant. 



(n) How do dimorphic plants differ from trimorphic plants ? Explain 

 what advantage (if any) the trimorphic plants will have over the 

 dimorphic plants. 



(12) Why are the pollen-grains larger in the short-styled flower of the 

 Primrose than in the long-styled form ? 



