454 THE SYMPETALAE 



days, during which time the umbels of imperfect flowers have 

 grown above them and assume such a position that when the 

 anthers finally open there results a rain of microspores upon the 

 stigmas below. 



The members of the carrot family are characterized by the 

 presence of essential oils and resins in the roots, stems, leaves or 

 especially in the fruits which usually contain oil cavities between 

 the ribs of the ovary. These substances are the sources of the 

 peculiar odors that make easy the recognition of these plants. 

 These oils give the commercial value to several fruits, as in the 

 caraway, parsley, fennel, anise, coriander. Several species con- 

 tain very poisonous alkaloids, as the water hemlock {Cicuta), 

 among the most poisonous of our native plants, and the hemlock 

 (Conium) which perhaps furnished the potion drunk by Socrates. 

 Several valuable food plants, as the carrot, parsnip, celery, par- 

 sley, are cultivated species of the family. 



Series h. Sympetalae. 



149. General Characteristics. — This group contains the most 

 common and abundant of our flowering plants, approximating 

 42,000 species, and ranks as the most specialized of the angio- 

 sperms. The variations of these plants have been very success- 

 ful and those are especially noteworthy that adapt them to the 

 most intelligent and active of the insects. As a result of these 

 advantages, they exceed all other groups in the number of in- 

 dividuals, though they comprise fewer orders as a consequence 

 of the striking uniformity in the floral structure. 



While a few of the simpler members of this group have dis- 

 tinct petals, the crowding of the organs on the receptacle has 

 resulted, in nearly all the forms, in a cohesion of the petals into 

 a sympetalous corolla, in the cyclic arrangement of the parts, and 

 in the reduction in the number of stamens, so that each whorl 

 does not exceed the number of petals, and more frequently one 

 whorl of stamens is partly or entirely suppressed. The pistils 

 are usually less numerous than the petals. The flowers range 

 from regular hypogynous forms to epigynous and irregular 



