GROSS ANATOMY OF FLOWERING PLANTS. XXXV 
rounded by the tubular sheath composed of adnate calyx, corolla, 
and andrecium. In some nearly related cases, in addition to the 
structures described above as perigynous, there is a complete 
fusion of the calyx, corolla, and stamen bearing tube with the 
gynecium, so that the ovule-bearing portion of the latter is 
below the rest of the flower. The perianth and the stamens are 
said to be evigynous in such flowers, and the ovary is inferior. 
(Fig. XXXV.) Some cases of epigyny are doubtless to be re- 
garded as due to the adnation of the calyx, corolla, stamens, and 
ovaries; in others the ovaries are adnate to the hollow axis which 
Fic. XXXVI.— Heterostyled flowers of Primrose, showing the long-styled form 
in the left-hand figure, and the short-styled form in the figure on the right. 
(From Darwin.) 
bears the perianth and stamens; in still others it seems probable 
that the hollow axis is itself ovule-bearing, and that the true 
carpels are borne on its summit. 
Certain terms descriptive of relations between the stamens and 
pistils which have recently come into use require explanation here. 
Relative Terms.—In many flowers the stamens and pistils do 
not mature at the same time—such are said to be dichogamous ; 
when the stamens mature before the pistils the flower is proter- 
androus ; and when the pistils mature before the stamens they are 
proterogynous, 
