Branched stone cells also occur in coto bark, acer spicatum, star-anise, witch-hazel leaf, hemlock, and wild-cherry barks. Non-branched stone cells are divided into two main groups, as follows: 1. Porous and striated stone cells, and, 2. Porous and non-striated stone cells. POROUS AND STRIATED STONE CELLS =Porous and striated= walled stone cells occur in ruellia root, winter’s bark, bitter root, allspice, and aconite. These stone cells are shown in Plate 33, Figs. 1, 2, 3, 4, and 5. The stone cells of ruellia root (Plate 32, Fig. 1) are greatly elongated, rectangular in form, with thick, white, strongly porous walls. The central cavity is narrow and is marked with prominent pores and striations. The stone cells of winter’s bark (Plate 32, Fig. 2) vary from elongated to nearly isodiametric. The pores are very large, the light yellowish wall is irregularly thickened, and the central cavity is very large. The pores are prominent. [Illustration: PLATE 31 BRANCHED STONE CELLS 1. Tea leaf (_Thea sinensis_, L.). 2. Witch-hazel bark (_Hamamelis virginiana_, L.). 3. Hemlock bark (_Tsuga canadensis_, [L.] Carr). 4. Wild-cherry bark (_Prunus serotina_, Ehrh.).] The stone cell of bitter root (Plate 32, Fig. 3) is nearly isodiametric. The walls are yellowish white and strongly porous and striated. The central cavity is about equal to the thickness of the walls. The stone cell of allspice (Plate 32, Fig. 4) is mostly rounded in form, and when the outer wall only is in focus it shows numerous round and elongated pores. The central cavity is filled with masses of reddish-brown tannin. The striations are very prominent. The diagnostic stone cell of aconite (Plate 32, Fig. 5) is rectangular or square in outline; the walls are yellowish and the central cavity has a diameter many times the thickness of the wall. The side and surface view of the pores is prominent, and the striations are very fine. POROUS AND NON-STRIATED STONE CELLS =Porous and non-striated stone cells= occur in Ceylon cinnamon, in calumba root, in dogwood bark, in cubeb, and in echinacea root. The diagnostic stone cells of Ceylon cinnamon (Plate 33, Fig. 1) are nearly square in outline; the walls are strongly porous and the large central cavity frequently contains starch. The stone cells of calumba root (Plate 33, Fig. 2) vary in shape from rectangular to nearly square, and the walls are greenish yellow, unequally thickened, and strongly porous. The typical stone cells contain several prisms, usually four. The stone cells of dogwood bark (Plate 33, Fig. 3) have thick, white walls with simple and branched pores. The central cavity frequently branches and appears black when recently mounted, owing to the presence of air.