44 PLANTS OF NEW ZEALAND 



and structure of the ilower depend to a large extent on the 

 method of poUination adopted by it. 



These methods are very numerous, and often very different, 

 and a great deal of complexity of contrivance, and apparent 

 purposefulness of action, is manifested by flowers in their 

 endeavours to secure effective pollination. If the pistil is 

 pollinated from its own stamens, it is said to be self-pollinated. 

 Darwin and others have shown, that, as a rule, seed obtained 

 from cross- pollinated flowers is healthier and more productive 

 than that from self -pollinated flowers. The result of continued 

 inbreeding is harmful to flowers as well as to animals ; but 

 there are probably more exceptions to this rule than was at 

 first supposed ; and in many plants there are special adapta- 

 tions for self-pollination. Cross-pollination may be brought 

 about by the action of wind or insects, or, more rareh', by 

 birds or other animals. 



The exact methods adopted will be discussed in connection 

 with specific cases. 



If stamens and pistil are found in one flower, it is said to be 

 hermaphrodite. If they are found on different flowers but on 

 the same plant, the species is then said to be itionoecious, but 

 if on different plants, it is termed dioecious. 



The Floral Envelopes. 



Surrounding the stamens are usually two floral envelopes. 

 The outer one is the calyx, and the inner is the corolla. The 

 corolla is usually brightly coloured, and serves as an organ of 

 attraction for insects and other animals. The individual 

 leaves of which it is composed are termed petals. They may 

 be free or united, regular or irregular in form, and, indeed, 

 manifest an infinite variety of shape, colour, texture and 

 arrangement. These characteristics depend almost entirely 

 upon the adjustment of the flower to the function of pollination. 



