Fig. 25, 83, 84.Holotype: Lyellia crispa R. Brown, Trans. Linn. Soc. 12: 5ti2. 1819.
Lyellia sens. str. [excl Philocrya aspera (I. Hagen & C. Jensen) Frye] has two species, L. crispa R. Br., occurring from Nepal eastward into Bhutan, and L. platycarpa Card, & Ther. in Yunnan.
An interesting feature of Lyellia crispa is the unique structure of the exothecium at the base of the capsule. The exothecial cells are anticlinally elongate, and have greatly thickened, deeply pigmented walls. In surface view, these cells appear to be isodiametric. Each of the stomata is surrounded by a ring of thinwalled cells and because of the sharp contrast between these cells and those of the surrounding exothecium, the stomata are conspicuous, even at low magnification. These "minute pores" are mentioned by Robert Brown in the original description of Lyellia!