Medicinal and aromatic plants – industrial profiles

Section 4: 
Pterostoechas
Ging.
Woody based perennials or woody shrubs with pinnatisect to bipinnatisect leaves with distinct
petioles. Bracts on axis of spike arranged in an opposite and decussate manner, subtending 
a single-flower with no bracteoles, giving a four-seriate (quadrate) spike. Subtending bracts 
ovate lanceolate in shape, with parallel veins. Calyx fifteen-nerved, bilobed the median posterior
tooth often distinctly deltoid, the other lanceolate in shape. Corolla bisymmetrical, twice 
the length of the calyx, five-lobed, the upper two erect and twice as large as the three lateral
lobes. Stigma bilobed. Nutlets elliptic, the lateral scar one-third the length of the nutlet,
mucilaginous. The important characters for distinguishing the species include leaf shape, 
indumentum, length of the bract subtending each flower and the shape of the upper middle lobe 
of the calyx.
The taxonomy of the genus 
Lavandula 
L.
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The largest section in the genus with at least thirteen species, distributed from the Canary
Islands, Cape Verde Islands, Madeira, across North Africa, parts of the Mediterranean basin, the
southern Arabian Peninsula and reaching Iran.
1 Median upper calyx lobe narrowly triangular in shape and 
 
equal in
size and shape to the other lobes  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 
L. coronopifolia
Median upper calyx lobe deltoid in shape, differing in size and shape to all
other lobes  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2 Whole plant with a silver grey indumentum  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Plants glabrous or with a sparse to dense indumentum of glandular and/or 
non-glandular hairs  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
3   Plant a low-growing shrub 20–40 cm. Bracts large, ovate in outline,
1.5
length of the calyx. Canary Islands and Madeira  . . . . . . . . . . . . . . . . . . . 
L. pinnata
Plant a robust shrub 50–100 cm. Bracts lanceolate to ovate/lanceolate in outline,
0.5–0.75
length of the calyx. Canary Islands (Tenerife)  . . . . . . . . . . . . . . . . . .  
L. buchii
4 Stems glabrous to glabrescent or very sparsely tomentose  . . . . . . . . . . . . . . . . . . . . . . .  5
Stems with a distinct indumentum of either short hooked stiff hairs, long white stiff
hairs, highly branched hairs, or short stalked glandular hairs or combination thereof . . .  7
5 Leaves pinnatisect to bipinnatisect. Leaves not fleshy  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
Leaves irregularly dissected, lobed or dentate. Leaves fleshy  . . . . . . . . . . . .   
L. rotundifolia
6 Plants woody at the base only, stems herbaceous. Bracts with
membraneous wings, orbicular-pentagonal in shape  . . . . . . . . . . . . . . . . . . .  
L. maroccana
Plants with woody stems, only the seasons growth herbaceous. Bracts 
without wings, ovate in shape  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
L. canariensis
7 Stem indumentum of short branched and long white stiff hairs, present at
least on the lower stem. Spike with a distinct twist  . . . . . . . . . . . . . . . . . . . .  
L. multifida
Stem indumentum of large branched hairs, short stalked glandular hairs
and/or stiff white non-glandular hairs or combination thereof. Spike
not twisted  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
8 Stems grey-green indumentum of large branched hairs. Leaves with deep
very regular pinnatisect divisions  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
L. minutolii
Stems with an indumentum of short stiff hairs, long white stiff hairs and/or short
stalked glandular hairs  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  9
9 Stem indumentum of short stiff hairs often hooked, with long stiff hairs. Glandular
hairs few. Bracts ovate with a long acuminate tip with three main nerves  . . . . . . . . . .  10
Stem indumentum of short stalked glandular hairs over white stiff hairs. Bracts ovate
lanceolate usually with five main nerves  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  11
10 Stem indumentum of short hooked stiff hairs, with occasional long stiff
hairs and short stalked glandular hairs. Algeria and Niger   . . . . . . . . . . . . . . . 
L. antineae
Stem indumentum of short stiff simple hairs often interspersed with longer
stiff hairs. Glandular hairs absent. Morocco  . . . . . . . . . . . . . . . . . . . . . . . . . .   
L. tenuisecta
11 Bracts at least the length of the calyx or exceeding it in length (1–1.5x)  . . . . . . . .  
L. mairei
Bracts 0.6–1
length of calyx  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  . . . . . . . . . . . . 12
12 Leaves distinctly 2–3 pinnatisect (lobed to midrib). Plant highly aromatic,
rather unpleasant aroma  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
L. pubescens
Leaves principally pinnatifid (lobed to only half the distance to midrib).
Plant aromatic with distinct smell of lemons  . . . . . . . . . . . . . . . . . . . . . . . . .
L. citriodora
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Tim Upson

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