Coalescence of parts of the same circle by their contiguous margins; and
Adnation, or the union of adjacent circles or unlike parts.
[257.] Coalescence is not rare in leaves, as in the upper pairs of Honeysuckles, Fig. [163]. It may all the more be expected in the crowded circles or whorls of flower-leaves. Datura or Stramonium (Fig. [246]) shows this coalescence both in calyx and corolla, the five sepals and the five petals being thus united to near their tips, each into a tube or long and narrow cup. These unions make needful the following terms:—
Gamopetalous, said of a corolla the petals of which are thus coalescent into one body, whether only at base or higher. The union may extend to the very summit, as in Morning Glory and the like (Fig. [247]), so that the number of petals in it may not be apparent. The old name for this was Monopetalous, but that means "one-petalled;" while gamopetalous means "petals united," and therefore is the proper term.
Fig. 246. Flower of Datura Stramonium; gamosepalous and gamopetalous.
