Revisional study of neotropical Beilschmiedia species (Lauraceae ...

Midrib. The most distinct character which discriminate neotropical Beilschmiedia species is
arrangement of the vascular bundles. The vascular bundles of the midrib are arranged in a
ring (with the upper part flattened) in B. a//oiophylla (Fig. 122), B. angustifolia (Fig. 124),
B. costaricensis (Fig. 127), B. curviramea (Fig. 128), B. hexanthera (Fig. 129), B.
immersinervis(Fig.131),B.latifolia(Fig.132),B.linharesensis(Fig.133),B. mexicana
(Fig. 134), B. obovatifolia (Fig. 136), B. ovalioides (Fig. 137), B. ova/is (Fig. 138), B.
pendula (Fig. 139), B. rigida (Fig. 140), B. riparia (Fig. 141), B. steyermarkii (Fig. 142) and
B. tovarensis (Fig. 143), while the bundles are arranged in a flattened arc in B .
angustie/liptica (Fig. 123), B. berteroana (Fig. 125), B. brenesii (Fig. 126), B. hondurensis
(Fig. 130) and B. miersii (Fig. 135).
Most of the bundles arranged in a flattened arc are united. On the other hand, most of
the bundles in a ring are diffuse to son1e degree. Less diffused bundles (into about two units
in the upper part, one in the lower part) occur in B. angustifolia (Fig. 124), B. curviramea
(Fig. 128), B. linharesensis (Fig. 133), B. rigida (Fig. 140) and B. riparia (Fig. 141), while
highly diffused (into more than ten parts) occur in the other species.
Metcalfe ( 1987) mentioned that medium-sized and small veins are often made vertically
transcurrent by sclerenchymatous elements, and that the sclerenchymatous sheath in a few
species of Persea spreads out beneath the adaxial epidermis. This is also seen in the midribs
of neotropical Beilschmiedia species. The vascular bundles are surrounded by
sclerenchymatous cells in all the species (e.g., Fig. 126), and the sclerenchymatous sheath
spreads out in B. angustielliptica (Fig. 123), B. costaricensis (Fig. 127), B. hexanthera(Fig.
129), B. hondurensis (Fig. 130), B . pendula (Fig. 139), B. riparia (Fig. 141) and B.
steyermarkii (Fig. 142). The sclerenchymatous sheath in B. berteroana and B. miersii is not
spread out, but thickened to more than eight layers.
The vascular bundles with sclerenchymatous sheaths are then surrounded by spongy
tissue, and gradually by collenchymatous tissue. In most of the species oil or mucilage cells
occur in the spongy tissue or collenchymatous tissue.
Discussion
To understand relationships within neotropical Beilschmiedia species with their leaf
anatomical characters, one of the most important prerequisites is that characters infom1ative
for the systematics are carefully selected. Therefore, which characters are informative is
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