Introduction mi 



have given rise to ihe various family types. These changes have come about I) the 



mucin of parts, especially petals and pistils; (2) by the reduction in number of stamens and 

 pistils, or the disappearance of one or more parts; (3) by changes in the form and 

 niont of puts, especially the petals; (4) by a change in level, in which the sepals become 

 united with the ovary, and the petals and stamens arc placed above it. Some of tl 



1 Oild-pinnate. 2 Tendril-pinnate 8. Even pinnate. 



changes appear in cue family, others in another. Few families show them all, and the 

 emphasis usually falls upon one of the four possible changes. The number of possible com- 

 binations is very large. This makes it clear why it is possible to get so many flower types 

 by modifying only four flower parts, sepals, 

 petals, stamens and pistils, in four different 

 ways. The three lines of evolution shown in 

 the chart (page x) arise from the simple but 

 tercups, and, passing through various family 

 types, end in the three highest groups, orchids, 

 mints and asters. In the orchids, the petals 

 are still mostly separate; in the mints, the 

 ovary is superior. In the asters, these changes 

 have been completed, and this group is con- 

 sequently the highest of the plant kingdom. 



4. Palmate or diuritate. 



6. Twice-pinr afe 



VI. Compound Leaves 



Certain families have a very distinct type of flower structure, while practically all have 

 some mark by which they may be told readily after some practice. The beginner should 

 start with those families which are most readily distinguished. Such are the pea. the lily, 

 the mustard, the aster and the grass families. From these one may advance readily to irids, 

 orchids, snapdragons, mints, buttercups, etc. The most convenient way of expressing a 



