A taxonomic revision of Cryptolepis R.Br. (Apocynaceae, Periplocoideae) in
southern Africa is presented. This revision comprises investigations into the
micromorphology of pollen, translators, leaf anatomy, leaf epidermal surfaces and
seed coat surfaces; macro-morphology of the plant parts; nomenclature,
geographical distribution and ecological characteristics of the six species indigenous
to southern Africa. The investigations resulted in descriptions with appropriate
nomenclature and the compilation of an identification key for the six species.
All available type specimens related to Cryptolepis in southern Africa were studied.
Where holotype specimens could not be located lectotypes were designated from
available isotypes or syntypes. Where no isotypes or syntypes could be located,
neotypes were declared. In cases where only syntypes had been given by authors of
species names, lectotypes were declared.
Cryptolepis is widely distributed throughout the northern parts of southern Africa,
with the largest concentration of species in the north-east of the region. Some
species, such as C. oblongifolia, are common, while others have very restricted
distribution ranges. C. delagoensis, for instance, is known from only six localities in
southern Africa. Only C. decidua occurs in the desert and semi-desert habitats in the
north-west of southern Africa, while the other five species inhabit savannah, sand
forest, riverine -, afromontane - and coastal vegetation in the eastern parts of the
region.
In southern Africa Cryptolepis consists of slender climbers, occasionally small
suffrutices or branching shrubs with white latex and interpetiolar ridges with dentate
colleters. Leaves are opposite, decussate or rarely fascicled. A combination of leaf
anatomy and leaf surface characteristics proved to be taxonomically useful for
distinguishing the southern African species. The fruit consists of paired follicles.
Seeds of Cryptolepis are adapted to anemochoric dispersal through a coma of hair
at the micropylar end. All southern African species can be differentiated from each other using cellular arrangement and primary and secondary sculpture of their seed
coat surfaces.
Floral characteristics are taxonomically useful for distinguishing Cryptolepis from
related genera. Cryptolepis is characterized by a distinct corolla tube, with corolla
lobes always longer than the corolla tube, corona lobes arising just above the middle
of the corolla tube, and usually included in the corolla tube, and stamens arising at
the lower third of the corolla tube, with interstaminal discs always present. Two,
semi-inferior, apocarpous ovaries are present. The styles unite to form a compound
style and pentagonal style-head, on which five translators are formed by epithelial
cells in grooves alternating with the stamens. The anthers are fused to the style
head, forming a gynostegium.
In the five species that occur in the eastern parts of the region flowers are arranged
in cymes. Prominent, paired colleters are found at the inner bases of the sepals. The
corona lobes may be oblong, clavate, deltoid or awl-shaped. The corona lobes are
always included in the corolla tube, where they touch or fit tightly, forming a dome
which closes off the lower corolla tube. Pollen characteristics and translator shape
are similar for all five species and have little taxonomic value.
C. decidua differs from the eastern species in that its flowers are solitary. The
colleters at the inner sepal bases are replaced by trichomes. The corona lobes are
filiform, do not form a dome over the lower corolla tube and may be exserted from
the corolla tube mouth. Pollen tetrad shape and translator shape and size differ
markedly from those of the other species. All these unique characteristics in C.
decidua suggest that this species may not belong in Cryptolepis.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-08252008-080208 |
| Date | 25 August 2008 |
| Creators | Joubert, Lize |
| Contributors | Prof HJT Venter, Prof RL Verhoeven, Dr AM Venter |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-08252008-080208/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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