280 



FLOWERS 



ered together in determining the relationships of a plant. 

 The flowers, however, are the most important and con- 

 venient means of identification. 



B. The Simplest Flowers. We can understand the 

 various kinds of flowers best by considering first the simplest 



kinds. The more 

 complex kinds 

 have evolved 

 from simple kinds, 

 from ancestral 



much like the 

 simple kinds 

 which exist to- 

 day. 



The simplest 

 flowers have no 

 perianth, and 



FIG. ico B. Flowers of the white ash (Fraxinus they are COm- 



Americana). A common and valuable tree whose j r essen ti a l 



flowers appear in early spring. They are very simple " 



and are of two kinds, nearly always borne on different parts Only. The 



plants, i.e. diclinous and dioecious. The picture 

 shows the end of a pistillate twig above and the end 



kinds of PS 



of a staminate one below. Of the two smaller pic- Sential parts are, 

 tures, the one at the left is a staminate flower, the one ^^ you knOW Sta- 

 at the right a pistillate one. 



mens and carpels. 



The simplest flowers of all are those which have only one 

 kind of essential part. In other words, the simplest flowers 

 of all are borne by plants which have two kinds of flowers ; 

 one kind is composed only of stamens, the other kind only 

 of carpels. In some cases, as in the duckweeds, a single 

 stamen or a single carpel is all that there is to the flower. 



