THE AUSTRALIAN GREY MANGROVE. 271 



well defined, the xylem and proxylem well pronounced, and 

 the phloem coloured purple by hsematoxylon being backed 

 by what is gradually becoming a distinct ring of stone or 

 sclerenchymatous cells, is followed by thin-walled wood 

 parenchyma cells enclosed the whole way round by a narrow 

 ring of original phloem, and this is subtended by a broader 

 band of cortex. Pores may be noted occurring in the 

 radial lines of the xylem. The whole is composed of a 

 perfect regularity of structure. 



(c) Figure 15. This shows a centre made up of vessels 

 and a few sclerenchymatous stone cells (in section) and 

 parenchyma, the whole bounded by a complete ring of 

 bundles, with numerous pores in the xylem (red) with 

 interfascicular rays, the phloem (purple) backed by short 

 sclerenchymatous cells followed by a band of wood paren- 

 chyma. Now this structure is repeated in a regular manner 

 outwards to the fourth ring, and then is noticed an intrusion 

 of another "ring" which breaks the continuity of the fifth 

 ring. This section is of particular interest because it shows 

 how, even in the early stages of growth, the rays are 

 restricted or limited to the space between the two walls 

 of sclerenchymatous cells, and so are not strictly medullary 

 rays as generally understood ; this feature obtains through- 

 out all the secondary wood in the species, and is more 

 fully illustrated in figure 16, (infra). Up to this stage, the 

 rings are entire and evidently annual, but from this out, 

 they become broken. 



Secondary Wood — Transverse Section. — (Plate XLII, 

 figure 16) In this section is seen a bifurcated band of thick 

 walled cells forming the barrier to the progress of the rays 

 to continue beyond the limits of each "ring." This wall 

 of sclerenchymatous cells is bounded on either side by wood 

 parenchyma with thin walls, and between these are the 

 wood fibres with small lumen. 



