412 BOTANY 



in many ways suggest the Alismaceee and allied families of apocar- 

 pous Monocotyledons, with which they are probably remotely related. 



More commonly, the stamens are equal to, or twice as many as, 

 the petals, and the carpels either the same or fewer. 



Reduction and Cohesion. In the further development of the flower, 

 the same tendency to reduction in the number of parts, and cohesion 

 of parts, seen in the Monocotyledons, obtains also among the Dicoty- 

 ledons. The carpels in the majority of them are more or less com- 

 pletely united in a compound (Syncarpous) ovary, and their number 

 is generally less than that of the other parts of the flower. There 

 may also be a more or less complete cohesion of the floral axis with the 

 carpels, so that an " inferior " ovary is developed, as in the Fuchsia. 



Cohesion of the sepals with the margin of the floral axis is very 

 common, and results in the cup-shaped or tubular calyx found in so 

 many flowers (Hollyhock, Carnation, etc.). In such forms the teeth 

 alone of the calyx-cup represent the sepals. While the showy part 

 of the flower is usually the corolla, this may be absent, as in Anem- 

 one and Fremontia (Fig. 432), where the calyx is brilliantly colored, 

 and mimics a corolla. Or, in other cases (Bougainvillea, Euphorbia), 

 the corolla is absent, and the flowers proper are inconspicuous, but 

 the inflorescence is surrounded by showy bracts, similar to the showy 

 spathe of the Aracese. 



Zygomorphy. Zygomorphy of the flower, exhibited in such 

 flowers as Delphinium, Tropoeolum, Pelargonium, etc., is also a form 

 of specialization, and like most of such adaptations, is directly asso- 

 ciated with the visits of insects. Where the petals remain separate, 

 the flowers are termed " Choripetalous." 



Sympetaly. The most specialized types of flowers found among 

 the Dicotyledons are those of the Sympetalae, in which the petals 

 are more or less completely united with a tubular outgrowth of 

 the floral axis into a cup-shaped corolla. Both hypogynous and 

 epigynous flowers occur among the Sympetalse, where a reduction in 

 the number of stamens (Labiatae, Schrophulariacese, etc.) is common, 

 and associated with strongly marked zygomorphy. The Sympetalze 

 are more numerous than the Choripetalae, and probably represent a 

 more modern type of structure. At the head of these are placed 

 the Composite, the largest existing family of plants. These show 

 a peculiar form of specialization which seems to have been 

 extremely successful. The individual flowers are usuallv small, but 

 are aggregated into dense heads, the outer (ray) flower being often 

 different from the central disk-flowers, and serving to render the 

 head conspicuous. 



The Fruit and Seed 



The Fruits of the Dicotyledons exhibit all the different types 

 known among the Angiosperms, and the same is true of the seeds. 



