Haworthia – Confusion Reigns Again (1986)

Printed in Excelsa 12:91 (1986)

Haworthia is a genus plagued by confusion of one kind or another and it seems now impossible to write about these plants without casting doubts on someone’s integrity or sanity.  The problem in the genus is not simply that there are very few herbarium specimens, or adequate descriptions and illustrations by which the various species can be typified. The various elements in the field are so continuously variable that it is difficult to decide where one species begins and another ends – but not so difficult.  There is some straightforward confusion as in the case of Haworthia margaritifera (L.)Haw. where Wijnands shows that H. pumila (L.)Duval is incorrect.  (Excuse my nomenclature – but this means it is incorrect for the species to which Duval attached the name [H. herbacea] – it is correct for the species to which Scott attached the name).

In the case of H. arachnoidea (L.) Duval there is no problem with the typification of the name, it is the application which is now a little confused.  When I first used the name in my Haworthia Handbook (1976) I did not elaborate on the application of the name other than to state that I based my interpretation of the name on the earliest illustration in Commelin’s Praeludia Botanica (t.27, p78, 1703).  Scott in Cact. & Succ. Jl US1 4:205 (1977) and in Aloe 16:41 (1978) maintains a different standpoint with the consequence that:-

H. herbacea (Mill.) Stearn sensu Bayer = H. arachnoidea sensu Scott.
H. arachnoidea (L.) Duval sensu Bayer = H. setata Haw. sensu Scott.

Unfortunately Scott does not specify this situation fully in his synonymy.  By stating “I cannot agree (with Bayer) that H. arachnoidea is synonymous with H. setata”, he implies that H. herbacea sensu Bayer = H. setata sensu Scott, which is not correct.

Scott (1978) presents a table of characters by which he separates his concepts of H. arachnoidea and H. setata.  This table is presented here together with those corresponding particulars which can be derived from the Commelin figure:-

Table 1.

It seems from this table that there are only two characters which can be quantified and equated with Commelin’s t.27.  These are the number of flowers and the number of flowers open.  Scott concludes that his arachnoidea more nearly equates the Commelin illustration.

There are at least 5 (other) illustrations in these older works which suggest an understanding of H. arachnoidea and Scott cites three of tem, namely DeCandolle Plantes Grasses t.50 (1799), Kerr-Gawler in Botanical Magazine t.756 (1802) and Salm-Dyck’s t.2 in the Monographia. Sect.12 (1840).  The illustrations in Botanical Magazine t.1361 and t.1417 (1811) are excluded by Scott as is direct citation of H. herbacea sensu Bayer from his 1977 synonymy (This of course suggests that he thought my interpretation of H. herbacea equated his H. setata).

The next problem is that of the flower.  The species to which Scott applies the name H. arachnoidea has in fact a most distinctive flower, having long arcuate buds with flattened fish-tail-like tips.  The open flowers have the upper petals in a very characteristic “cowboy hat” fashion.  (This is also the case in H. reticulate and accounts for the name H. subregularis  meaning the flower was “almost regular” because the effect is to make to flower appear more symmetrical than is usual in the two-lipped flowers of the genus.  It is extremely difficult to convey meaning in this respect when botanists who dabble in Alooid taxonomy persist in their convictions that these zygomorphic flowers are generic markers when most of the Alooids actually have such two-lipped flowers).  This characteristic does not appear in Commelin t.27.  It is also a feature in H. reticulata and one just has to ally the two species on this character and on distribution.  (It is surely significant that this bifid bud is also prominent in the Retusae).  Interestingly enough Scott recognises Jaquin’s Aloe pumilio as H. reticulata but an almost identical illustration (C478) from the Kennedy Catalogue of Pictures in the Africana Museum he identifies as H. marginata which has a wholly different inflorescence.  Similarly he identifies C481 as H. venosa despite the inflorescence being out of character with that species.  Col. Scott abandons (1985) the subgeneric division based on floral characters on the grounds “that taxonomy is largely a visual discipline”!

Then the question of hybridization is introduced.  This argument is simply introduced too often to be taken a seriously as it is.  (I know this because initially I made the same ‘mistake’.H. herbacea is quite common in the Worcester/Robertson Karoo where it is intimately related to H. reticulata, having practically the same inflorescence and flowering time.  There are several populations which blur the difference between the two species and one (at least two – Orange Grove and Ribbokkop) where there are putative hybrids.  H. arachnoidea (Scott’s H. setata and a name I also used at one stage) is a relatively widespread species and hybrids with H. truncate, H.graminifolia and H. blackburniae have been observed.  The species is less common in the Worcester/Robertson Karoo.  This is an area I know well and I have only once collected H. arachnoidea in close proximity to H. herbacea and have not seen any plant that I could possibly consider to be a hybrid of these two species nor any herbarium specimen to substantiate such a hybrid.  The species flower at different times (H. herbacea Sept-Oct., H. arachnoidea Nov.-Dec.) and in my opinion it is highly unlikely that they could hybridise in the wild. (Since this was written I become aware of several localities where the species are in proximity but not sharing habitat nor evidence of hybrids. It would be really interesting to know if anyone has ever succeeded in hybridizing the two species).  Col. Scott’s distribution maps reflect a degree of geographical inaccuracy ad H. herbacea is rarely found in Fynbos communities or on pH6 soils (pH is practically never cited on any collecting record).  It is associated with Malmesbury and Bokkeveld shales (and Karoid vegetation).

It has already been shown in the table that Scott’s concept of H. arachnoidea does not agree with the illustration selected as the type of the species.  (Here it really means the type for the name).  Furthermore, his description of the flower does not agree with that field element to which he applies the name.  H. herbacea has large flowers which are usually beige coloured with pinkish tips.  Uitewaal applied the name “luteorosa” to the element to suggest a yellow-pink colour.  A Villiersdorp population has very large pinkish flowers.  The petal mid-veins are never green.  In the intermediate populations impinging on H. reticulate the flowers can be white.

There is a problem in the typification of the name H. herbacea because it is typified by an ancient Boerhaave illustration.  I used the name because it was available.   The flower here also does not agree with that species to which the name is applied.

(In fact W.T.Stearn also fouled the playing field.  I am sure if he had known the plants at all – and this is where nomenclature freaks can wreak havoc – he would have ensured the perpetuation of the epithet atrovirens as the type of herbacea is more probably illustrative of H. maraisii.  I must admit that I lose the plot when it comes to this juristic juggling and why I eventually revised Haworthia on persuasion rather than conviction.  It would in my opinion be really silly to now change names again.  The problem of this use of names and identification of H. arachnoidea and H. herbacea continues to the present day.  I find it curious that despite even the publication of this article and one which preceded it, the facts on which they were based, and then my revision, the confusion persisted and I wonder if further debate in Haworthiad ever resolved the issue.).