POLLINATION AND FERIILIZATION 121 
6. Obtain some cleistogamic flowers of Violet and examine 
these. 
QUESTIONS ON CHAPTER VIII. 
1. Make a drawing to show the structure of an ovary with 
its style and stigma, and of an ovule contained in it at the time 
of fertilization, and indicate the course of the pollen tube. Label 
the different parts in your drawing ; no further description of it 
need be given. 
2. What is the difference between pollination and fertiliza- 
tion? Write brief descriptions of flowers whose structure 
favours: (a) pollination by wind; (b) pollination by insects. 
Name two examples of (a) and three examples of (b). 
3. What is meant by pollination? Distinguish carefully be- 
tween self-pollination and cross-pollination. Choose any flower 
you have studied which contains honey and is pollinated by 
insects, and state: (a) Where the honey is formed ; (b) how 
insects in obtaining the honey touch the pollen and stigmas; 
(c) the adaptations favouring cross-pollination: (d) anything 
else of interest you know about the pollination of the flowers 
selected. Make a sketch of the flower as seen in longitudinal 
section to show the pollination-mechanism. Name the flower 
you select. 
4, Explain the peculiarities of the following kinds of flowers ; 
Trimorphic; cleistogamous; ornithophilous. Mention as many 
examples of each kind as you know. 
5. Describe the structure of an ovule and three typical 
forms which it may assume. Mention for each form at least 
one plant in which it occurs. Give, with reference to some 
familiar example, an account of the changes which an ovule 
undergoes to form a ripe seed, 
6. Give an account of the structure and function of a pollen 
grain. 
7. Explain clearly the biological significance of (a) brightly 
coloured, (0) irregular, (c) regular, and (d) inconspicuous flowers. 
8. Of what advantage is cross-pollination to a plant? De- 
scribe three mechanisms which you have observed in flowers, 
which aid in effecting cross-pollination, Name the flowers you 
choose and give sketches, 
