The beak is made up of horny elements, like the labial teeth, fused together; its edge, when sufficiently magnified, is seen to be denticulate, each denticle representing the cusp of a single tooth.
Betulina, the leaves of which are cuneateobovate, with denticulate margins.
This sexually immature stage, regarded at one time as representing a distinct species and named Linguatula denticulate, is reached in about six or seven months and measures from 6 to 8 mm.
The " postabdomen," marked off by the two postabdominal setae, usually has teeth or spines, and ends in two denticulate or ciliate claws, or it may be rudimentary, as in Polyphemus.
Besides this, P. Sieboldii (cortusoides amoena), I ft., originally deep rose with white eye, but now including many varieties of colour, such as white, pink, lilac and purple; P. japonica, to 2 ft., crimson-rose; P. denticulate, ft., bright bluish-lilac, with its allies P. erosa and P. purpurea, all best grown in a cold frame; P. viscosa, 6 in., purple, and its white variety nivalis, with P. pedemontana and P. spectabilis, 6 in., both purple; and the charming little Indian P. rosea, 3 to 6 in., bright cherry-rose colour, are but a few of the many beautiful kinds in cultivation.