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Transactions. 



enormously thickened by depositions of cellulose.* The secondary xylem 

 is not all lignified, but consists of strongly lignified spiral vessels, inter- 

 spersed among prosenchymatous elements with thick cellulose walls. 



(6.) Leaf. — The leaves are arranged decussately in opposite pairs. They 

 are about 3 mm. long, subulate, pointed, slightly curving inwards towards 

 the axis. In section they are semicircular, with broad sheathing mem- 

 branous bases, and resemble very much the leaves of Raoulia Haastii. 

 The general colour is a light yellowish-brown, and in winter a small amount 

 of anthocyan occurs in the edges of the sheath near the commencement 

 of the subulate part. 



The rosettes much resemble those of R. Haastii, but the leaves are not 

 so closely appressed to the axis, and the tips are more acute. About 

 twelve leaves are visible from above. 



Transverse sections of the subulate part of the leaf show the following 

 anatomical structure : — Epidermis : There is a very thick cuticle, which is 

 rather uneven and ragged on the exterior, and as thick as depth of epidermal 



j~ crystal 



stereor/ie 



Fig. 12. — -Transverse section of leaf of Sclera nthus biflorus. 



cells. Epidermal cells very regular. Stomata : Guard-cells as large as epi- 

 dermal cells ; walls thick ; level with cuticular surface ; on all surfaces of 

 leaf. Chlorencliyma : Cells show practically no differentiation ; ellipsoid 

 or cylindrical, and rather loosely packed. Air-spaces fairly abundant, and 

 many are large ; a definite air-space below each stoma. Chromatophores in 

 all cells save those of the bundle-sheath ; large, ovoid, green to yellow, with 

 many granules. The granules vary in number, are strongly refractive, and 

 are apparently of a brownish or reddish colour, but are so minute that 

 accurate observation is difficult ; probably they are oil-drops. They are 

 most numerous in older leaves : here the plastids are yellow ; in young 

 leaves the plastids are green. Most likely these globules, if oil-drops, may 

 represent degeneration products of the chloroplast. Crystals : Large crystal 

 aggregates of calcium oxalate occur in large cells close to midrib. These 



* In old stems the cell lumina are almost obliterated. The cells are about twice 

 as long as broad, and their walls take on a faint violet colour with chlor-zinc-iodine. 



