364 



BOTANY 



Somewhat more specialized flowers are the " Apocarpous," flowers 

 with well-developed perianth, such as Asimina (Fig. 313), but all 

 of the floral leaves quite separate. These simple 

 flowers, too, may have the number of parts indefinite, 

 and are often radially symmetrical, or actinomorphic. 

 As flowers become more specialized, the parts 

 become definite in number, and there is a tendency 

 to reduction in the number of parts, and to cohesion 

 of the floral leaves. Thus in the members of the 

 Lily family the flower is made up of several three- 

 leaved whorls, the three carpels being united into 

 a compound pistil. In most Dicotyledons there is 

 also a difference in the character of the sepals and 

 petals, and the former are grown together into a 

 cup-shaped or tubular calyx, as in Dianthus. 



FIG. 329. A, umbels of Aralia racemosa. B, head of Anthe- 

 mis cotula ; r, ray-florets. 



In such highly specialized flowers as the Orchids 

 (Fig. 338, C), the reduction and cohesion of the 

 parts is carried to the extreme. Of the six stamens 

 of the more generalized Monocotyledons, only one is 

 left, and the base of the perianth-tube is coherent 

 with the base of the carpels. Moreover, the single 

 stamen is united with the upper part of the pistil 

 to form the peculiar structure known as the " Col- 

 umn," or " Gynostemium." Where all of the parts are 

 free from the ovary the flower is " Hypogynous " ; 

 where the ovary is more or less completely adherent 

 to the floral axis, " Epigynous," or " Perigynous." 



In the reduction of parts in the dicotyledonous 

 flower the carpels are the first to diminish, the num- 

 ber of carpels being less, as a rule, than that of the other floral 

 leaves. Where the flowers are markedly zygomorphic, or bilaterally 

 symmetrical, like the lipped flowers of the Foxglove or Sage, the 

 stamens are less in number than the corolla lobes. In the less 



: in 



FIG. 328. Spike 



of Plantain. 

 (After BAILEY.) 



