Biology
Lavatera oblongifolia stem in bud © Christopher J S Davis
Lavatera oblongifolia is a small perennial shrub 60 – 150 cm tall, branching from a woody base, with erect, turning stems. Its upper leaves are generally erect and more or less folded, while lower leaves are patent.
It bears single flowers in the leaf axils of indeterminate flowering stems, which are entirely homologous with determinate flowering stems in closely related species such as Lavatera olbia – although these are often described as ‘leafy inflorescences’. The fasciculate axillary inflorescences of species such as Lavatera triloba represent a multiplication of these. The epicalyx in Malvaceae (Malvoideae) is understood to be derived from the involucral bracts of an ancestral cymoid inflorescence reduced to a single flower.
Its diploid chromosome number is 42, which is presumed to be derived from hexaploid ancestors, as the base chromosome number for Lavatera is 14 – as found in the type species Lavatera trimestris.
Description
The leaves are:
- entire, up to 7.5 by 4 cm
- ovate-lanceolate to oblong-ovate
- cordate or rounded at the base
- apex acute or sub-acute and margin crenate-dentate
- very prominently veined underneath
The petioles are up to 15 mm, and much less than half as long as the blade
The stipules are:
- 4 by 12 mm
- ovate-lanceolate, acuminate
- falling early
The flowers are:
- solitary in the leaf-axils
- much shorted than the subtending leaf
- borne on stout pedicels
- equal in length to the calyx, up to 15 mm
The petals are:
- widely obovate, truncate
- tip obcordate, emarginate
- 1.5 – 2.5 cm long
- pink with bases marked purplish
The calyx is:
- 15 – 20 mm long
- erect in fruit
Sepal lobes are:
- 10 – 12 mm long
- narrowly triangular
- lanceolate, acute
The bracteoles are:
- fused into an epicalyx
- free lobes 6 – 8 mm
- lobes broadly triangular, obtuse
- sometimes toothed or notched
- about half as long as the sepals
The fruits are schizocarps divided into 16 – 20 mericarps.
The mericarps are:
- finely papillose
- generally glabrous, or with a few fasciculate hairs at the apex
- light-brown
- dorsally smooth, rounded
- lateral faces smooth
- lateral margin obtuse
- loosely covering and falling freely from the seed
The seeds are brown, asymmetrically oblong and kidney-shaped.
