KEY FOR IDENTIFICATION OF GUIANAN GENERA

1Rays partly very wide (over 10 cells) and very high; stems without included phloem.
1'Rays narrow, inconspicuous; stems generally with included phloem, either as isolated islands or as concentric bands, in some species without included phloem.
2Woody cylinder stron ly indented by the thick bark (cross section); wide rays hardly contrastmg in colour with the ground tissue.
2'Woody cylinder not indented by the thin or moderately thick bark of even width; rays conspicuous by contrasting colour.
3Wide rays without unlignified cells.
3'Wide rays with 1-4 rows of unlignified cells at the margin of the growth rings.
4Silica bodies abundant in ray cells; stems with a red exsudate.
4'Silica absent, crystals often abundant in ray cells; stems without red exsudate.
5Vessels moderately numerous, from 15-40(100) per sq. mm, radial multiples always present.
5'Vessels rather few, less than 15 per sq. mm, radial multiples rare.
6Septate fibres conspicuous, numerous, in one cell wide concentric bands.
6'Septate fibres present but generally scattered among the fibre-tracheids, often rare and difficult to observe.
7Crystals numerous, mainly in the unlignified ray cells and in sheathing ray cells.
7'Crystals not very numerous, in random distribution.
8 Included phloem absent.
8'Included phloem present.
9Included phloem present as scattered strands; usually low trees.
9'Included phloem in different arrangement; lianas or shrubs.
10Strands of included phloem arranged in concentric rings; lianas.
10'Included phloem in narrow concentric bands, with or without radial or oblique connective tissue.
11Included phloem in concentric bands, without interconnections.
11'Included phloem rings interconnected radially or obliquely.