FLOWERS AND THEIR USES 259 



directly concerned as are the stem, leaves, and roots in the 

 plant's relations with the world outside. 



Flowers, to be sure, have undergone changes during the 

 millions of years that seed plants have existed ; if this were 

 not true, there would not be the great variety of flowers that 

 we now find. But these changes have gone on much more 

 slowly than have the changes in vegetative organs, and so 

 all the members of a family may have kept very much the 

 same flower structure, although in other ways they have 

 come to be very different from one another. This is why 

 the structure of flowers is so useful in fixing relationships. 

 For example, the apple, the raspberry, the strawberry, and 

 the rose are members of the same family. Their relation- 

 ship is shown by the structure of their flowers ; but one would 

 hardly suspect it from an examination of their other parts. 



270. Staminate, Pistillate, and Perfect Flowers. — In 

 ■classifying angiosperms, we try to determine which of the 

 many kinds of flowers are most 



primitivs — that is, are most like f'^il'lnnT " 



the flowers of the original ancestor ^-\^\i|ffljA>-i^" '* 

 or ancestors of the angiosperms — / ,. ^^m^x:~ — '^"' 

 and which have departed farthest CL_..^^'^,^^^^°^ — <i 



from the original condition. In a ^ [m-j « 



general way, it appears that the \f- / 



original angiosperm flowers were ^^^ ^^^ _^ lengthwise 

 much hke the cones of a pine, and section through the flower of 



that in the course of time advances an apple (a perfect flower) ; 



have been made from this condi- <^> sig™^^' > '^'J ^''^' '^' 



petal ; a, a sepal ; e, ovary 



tion in several different directions, with ovules; /, flower-stalk. 

 For example, angiosperm flowers 



seem to have been at first of two distinct sorts — staminate 

 and pistillate. Many angiosperms of the present day, like 

 the cucumber and the Indian com, still have separate stami- 

 nate and pistillate flowers. In this respect, the cucumber 

 flower is more primitive than a flower which, like that of the 



