Some are enclosed within the tube of the flower, as in Cinchona (included); others are exserted, or extend beyond the flower, as in Littorella or Plantago.
They are hypogynous, and have long and very delicate filaments, and large, linear or oblong two-celled anthers, dorsifixed and ultimately very versatile, deeply indented at each end, and commonly exserted and pendulous.
E, Surface view of the shell with gill-tentacles exserted as in a, Mantle.
The four succeeding sections, in which the ovipositor is modified into a sting (always exserted from the tip of the abdomen) and the trochanters are with few exceptions simple, form the Aculeata of Linnaeus.
They are succeeded by succulent fruits, which are exserted, and frequently scaly or spiny, in which respects this genus differs both from Melocactus and Mammillaria, which have the fruits immersed and smooth.