126 



INTRODUCTION TO BOTANY 



115. What is a flower ? A hasty examination of an ordinary 

 flower does not give much evidence as to the relation which its 

 organs bear to the parts of the plant already studied ; that is, 



to the root, the stem, 

 and the leaf. There 

 is, however, plenty of 

 evidence to show that 

 the fewer is a 



ntlior- 



FIG. 102. 



B 



live-forever 



wise modified 



(Sedum) 



A, entire flower, B, lengthwise section ; carp, 

 carpels; stam, stamens; pet, petals; sep, sepals. 

 An excellent example of a flower in which the 

 parts of each circle are of the same number and 

 all separate. Somewhat enlarged. After Schimper 



duction of seed. The 

 floral organs therefore 

 correspond to leaves. 

 One of the most easily 

 understood evidences 



of the branch-like character of the flower is the fact that 



the positions of the flower buds on the branch are similar to 



those of leaf buds ; that is, they are usually either axillary or 



terminal. Moreover, in its earliest 



stages a flower bud is developed 



much as a leaf bud is. 



116. The arrangement of the 



organs of the flower. The floral 



organs spring from the receptacle, 



an expanded portion of the flower 



stalk. Sometimes, as in figure 102, 



the receptacle is but little enlarged ; 



sometimes, as in figure 103, it is 



much enlarged ; often it is convex 



or concave. Usually in dicotyle- 



dons the floral organs are arranged 



in whorls, or cycles (that is, in circular fashion), on the recep- 



tacle, but sometimes part or all of them are in spirals. In case 



there is the same number of parts in each cycle, each part 



commonly stands opposite a space between two members of the 



rec 



FIG. 103. Lengthwise section 

 of flower of a buttercup 



carp, carpels; pet, petal; sep, 

 sepal ; rec, large convex recep- 

 tacle on which the numerous 

 carpels are borne. Somewhat 

 enlarged. After Baillon 



