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evolution of flowers two processes have been constantly at 

 work, ever changing and obscuring things. There has 

 been a constant advance in many different lines of descent, 

 from the simple to the complex. At the same time, in afi 

 sorts of different genera and families reduction processes 

 have taken place that have tended to reduce flowers from 

 a complex to an apparently simple type. Both the advance 

 and reduction are results which we are obliged for the 

 present to refer to as changes induced in response to 

 changes of environment. These two processes of advance 

 and reduction have not taken place in progressive series, 

 but have constantly oscillated in response to ever-changing 

 conditions. The result is that it is no easy matter to 

 unravel the line of descent of any form. We are con- 

 stantly grouping together beings whose structure appears 

 to denote a like descent, and very often erroneously. There 

 is always one conservative feature tending to restrain, and 

 that is the possible response the being can make. Every 

 individual plant of one species differs from its fellows. It 

 has its own constitution, with its own limited range of 

 response, and no change of surroundings can cause it to 

 respond in excess of that range. If such is necessary, the 

 only response left to such an individual is to die. 



The habits observed in this family, namely, short-lived 

 herbs and long-lived climbers, show that habit is no test 

 of relationship. Some families consist wholly of shrubs, 

 others of trees, while others may contain all conditions. 

 Neither must the shape of the leaves be relied upon. 

 These organs are developed for a special purpose, namely, 

 to increase the extent of green surface exposed to sunlight, 

 and are variously formed according to the possibilities 

 of the plants and the surroundings in which it may find 

 itself. The same shaped leaf may be found in different 

 families, or many shapes in the one. On the other hand, 

 in some cases the leaf may be constant in general features 

 and be indicative of a particular group. The development 

 of leafy structures is of great advantage, and may arise 

 in any plant, whether seaweed, moss, or higher plant, 

 without indicating descent one from the other. It is only 

 an indication that an advantage may arise and be trans- 

 mitted in any cycle of affinity. 



