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PHYCOLOGICAL SOCIETY OF AMERICA
Botryoglossum farlowianum
(or is it really?)
While Botryoglossum has received little press or regards in the scientific world, the one area in which a considerable interest has been shown it is taxonomy. The name Botryoglossum has caused much furor and produced a good amount of contrary research, as many are convinced that B. farlowianum is in fact a member of the related genus Cryptopleura.
So what's all this furor about? The history begins in 1843, with F.T. Kutzing's work, Phycologia generalis. In this volume, he erects the genera of Botryoglossum, though his specimen hails from South Africa. In 1872, J. Agardh, to whom credit is given for naming B. farlowianum, recognized seven species under this heading. Works by J.B. DeToni, in 1900, and H. Kylin, in 1924, transfer Agardh's designations into their current taxonomic positions. Much of the trouble with B. farlowianum may have arisen from the fact that, as Botryoglossum was originally identified in South Africa, matching of samples across such a geographical divide often is an unsure process.
The main controversy over B. farlowianum is its similarity to species of the genera Cryptopleura.
Cryptopleura violacea Botryoglossum farlowianum
In Kutzing's original work, the descriptions of the two genera did not make clear enough distinctions between the two. He described Botryoglossum as: thalli with midribs, leathery, tetrasporangial sori on pedicellate proliferations which may be marginal, in axils of branches, or in rosettes on the thallus surface. Cryptopleura he described as: thalli without midribs, minutely veined. With such sparse descriptions, it isn't surprising that taxonomists and beachcombers continue to be confused.
While the distinction made by Kutzing in the presence/absence of a thallus midrib might seem to be definitive, it isn't necessarily. Cryptopleura has been known to also exhibit a thick midrib, similar to that found on Botryoglossum, although often this is just thickened by the concentration of tissue in a thinner stipe, not by an actual prominent midrib. This feature, while somewhat useful, does not always hold true.
So what are the absolute distinctions between Cryptopleura and Botryoglossum? In 1983, Juliana Ver Steeg and Michael N. Josselyn conducted taxonomic and morphological study of these differences, entitled Taxonomic and Morphological Studies of Cryptopleura (see references for citation). Their conclusions seem to make my website completely pointless, as they decided that B. farlowianum should in fact be classed as Cryptopleura farlowianum, though they do indicate that more study is needed to confirm this.. To see a pictoral comparison of their work, click here .
The main way to distinguish between the two genera was shown to be the origin and shape of tetrasporangia, in combination with margin morphology. There is also some differentiation in marginal proliferation appearance.
In my own studying of herbarium specimens from the central California coast, and elsewhere, it seems to me that both B. farlowianum and B. lobulifera, a fellow Botryoglossum, are easily distinguishable from the many Cryptopleura species which I compared them to, although I believe that some of the samples may have been labeled incorrectly. Though I must admit that through my personal experience of looking for beach-wrecked Botryoglossum, there was often a great deal of unsurity about the veracity of the identity of my finds, even to a semi-experienced eye such as mine.
Currently, Botryoglossum is holding up under the pressure, remaining recognized as a true genus, though if more research is conducted in the future, this may change, as is the way with algal taxonomy.
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© 2001 Shasta Daisy Pistey-Lyhne . All rights reserved.