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Afrikaanse Inligting
Those Problematic Spiderheads
Se gremialis and Se
acrocarpa
The difference between the Riviersonderend and Common Rootstock Spiderhead has long stymied atlassers. John Rouke points out that they are totally different – a glance at the rounded pollen presenter of Se acrocarpa should immediately distinguish it from Riviersonderend Spiderhead - Serruria gremialis with its cylindrical pollen presenter, ringed at the junction with the style. Other useful (but less reliable) features are more obvious in the field: Se acro tends to have yellow (seldom silvery pink) petals and it tends to be more erect (rather than sprawling). The leaves also have more of a stalk (rather than a very short stalk).
So, using this rule of thumb, we find Se gremialis on the Stettynsberg and both north and south slopes of the Riviersonderend Mountains, reaching somewhere near Stormsvlei. Se acrocarpa occurs south of the Riviersonderend Mountains (indeed on its lower slopes) and on the flats almost to Heidelberg, where it extends from Potberg to the Langeberg in Fynbos patches.
Will atlassers please sort out the details of the distribution of these two species – spring and summer are ideal for collecting herbarium material for any form of either species found outside the ranges mentioned above. Details can be found on the Web.
And now that this problem is solved, comes the next problem. An intermediate between Se acrocarpa and Se balanocephala has been found near Montagu. Given that the only real difference between the two species is the growth habit, can these be treated as separate species?
Tony Rebelo
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