| BEN |
| BOTANICAL ELECTRONIC NEWS |
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| ISSN 1188-603X |
| No. 278 December 8, 2001 | aceska@freenet.victoria.tc.ca | Victoria, B.C. |
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Protecting Canada from the costs of introduction of alien species and contributing to the control of alien species is essential to protect the Canadian economy, environment and biodiversity. Protection is dependent upon accurate identification. This communication, developed in connection with a request from the Canadian Food Inspection Agency, facilitates the identification of an aquatic plant that is increasingly being used in the aquarium trade, but is not likely to be correctly identified with tools currently available.
It may have been through use in malaria eradication programs that Egeria densa Planchon became a widespread aquatic weed. It was promoted as an "oxygenator" in fish culture which was considered very important in reducing mosquito larvae which in turn reduced the threat of malaria. Later it was promoted as an attractive plant of water gardens and for use in aquaria. It was also widely spread through use in experimentation and botany teaching because of the ease of viewing cytoplasmic streaming through the leaf lamina that is only two cells thick. It soon became naturalized in cool subtropical and warm temperate regions worldwide. In Canada it has persisted after introduction in Vancouver and on Vancouver Island (Catling and Wojtas 1986). The native range of the two species in the genus Egeria is restricted to a relatively small region of South America centering on southeastern Brazil (Cook and Urmi-Konig 1984).
In contrast to Egeria densa, E. najas Planchon is much less well known. It has been used as an aquarium plant almost worldwide, but has apparently not become established outside its native range, although it has been reported as "spreading in aquarist circles" (e.g. Müuhlberg 1981). Egeria najas is currently listed for sale by a number of US aquarium plant suppliers under the scientific name and/or the common names "Narrow leaf Anacharis" and "Light Green Anacharis." One advertisement reads "Egeria najas - large new algae buster, $ 2.00 US per stem." "Algae busters" are "stem plants" that grow quickly and outcompete algae for nutrients contributing to a better aquarium display.
Recently (26 November 2001) unidentified material of Egeria najas arrived at the Canadian border from Singapore with a question: was it Hydrilla verticillata (L. fil.) Royle? Prior to the production and dispersal of a pamphlet (Jomphe and Catling 1994) that facilitated identification of aquatic weeds entering Canada, both Egeria densa and Hydrilla verticillata were submitted to the authors for identification frequently, and both species are still received from time to time, mostly in the form of fragments, but we had never before encountered Egeria najas.
The question posed by the border authorities was actually a very relevant one because Egeria najas looks a little more like Hydrilla verticillata than like its closer relative E. densa. The leaf serrations of E. najas are conspicuous and easily seen without magnification, like those of Hydrilla verticillata, and quite unlike the leaf serrations of Egeria densa which can be seen only with magnification. Therefore Egeria najas could be easily identified as Hydrilla verticillata. This potential problem is actually much more serious than it may seem because most of the available literature (e.g. Crow and Hellquist 2000, Haynes 2000), including for that matter our earlier identification pamphlet (Jomphe and Catling 1994), only offers a choice between Egeria densa and Hydrilla verticillata without any mention of Egeria najas. This is of course because it has not become naturalized outside its restricted South American range. Crow and Hellquist (2000) separate vegetative Egeria from Elodea by leaf length, the former having leaves 12-40 mm long, the latter with leaves 6-17 mm long. This is a useful, but obviously overlapping character, and material of Egeria najas could be keyed to either E. densa if it had longer leaves or Hydrilla verticillata if it had relatively shorter leaves.
Although Haynes (2000) does not mention E. najas, his key separating Egeria and Hydrilla would result in identification of E. najas correctly in the genus Egeria because the combination of orange-brown hairs on the intravaginal squamules and abaxial midvein of leaf with prickles is relatively distinctive for Hydrilla verticillata. Although relatively distinctive, these characters are rather obscure. The intravaginal squamules (squamulae intravaginales) are scale-like structures on the upper leaf surface where it joins the stem (the leaf axil), but they are only 0.5 mm long, and high magnification under a microscope is necessary to see the fringe. The prickles on the midvein are also not easily observed, but most importantly they are not always present. Cook and Lüond (1982) indicate that H. verticillata "occasionally" bears spines on the on the abaxial (under) surface.
Thus one has to be familiar with the plant, or to have books on aquarium plants, in order to be able to identify Egeria najas. Having aquarium plant books is not always the answer because E. najas is not included in many of them, and in many cases there is only a passing mention without any details on identification. Egeria najas is included in only 3 of 13 major books on aquarium plants published since 1986.
Botanists may encounter Egeria najas with increasing frequency - without knowing it. Even when it is considered there is still a problem because existing keys to Egeria rely on flowering material, whereas botanists often receive vegetative material for identification. The following key, which we developed largely for vegetative material, should prove helpful in identification of Hydrocharitaceae with whorled leaves.
1. Leaves with obscure serrations or marginal prickles (requiring magnification to be readily observed) and leaf edges straight ........................... Egeria densa and Elodea spp.
1. Leaves with prominent serrations or marginal prickles (readily seen without magnification) and leaf edges conspicuously concave or straight between the serrations.
2. Leaves long-attenuate, concave between the serrations, their midvein without prickles on the abaxial (lower) leaf surface; scales in the leaf axis absent or to 0.36 mm long, mostly smooth-margined and lacking a fringe of orange-brown hairs; internodes mostly much shorter than the leaves and up to 10 mm long 1 dm below the growing tip; flowers with round petals and with nectaries .......................................... Egeria najas
2. Leaves linear to attenuate, straight to slightly concave between the serrations, their midvein sometimes with prickles on the abaxial (lower) leaf surface; scales in the leaf axis mostly ca. 0.5 mm long, mostly with a fringe of orange-brown hairs; internodes mostly as long as the leaves and up to 50 mm long 1 dm below the growing tip; flowers with linear petals, lacking nectaries ................................ Hydrilla verticillata
The specimen of E. najas that arrived from Singapore had a single female flower with petals 5 mm long and 4 mm wide, and staminodia less than 0.5 mm long. All leaves were less than 1.5 mm wide. The most recently produced detailed descriptions of the three species discussed above are in the revisionary works of Cook and Urmi-Konig (1984) and Cook and Lüond (1982) and in the earlier Cook et al. (1974).
References:
This massive work devotes 1197 large-format pages to 75 families sensu lato and innumerable genera, with another 45 pages on 36 "families of questionable toxicity or [toxic] significance" (the title of chapter 77). The non-angiosperm families treated are: Cupressaceae, Cycadaceae, Dennstaedtiaceae, Equisetaceae, Ginkgoaceae, Pinaceae, Pteridaceae, Taxaceae, Zamiaceae, and the questionably toxic Dryopteridaceae and Ephedraceae.
Some families have extensive bibliographies, as 26 pages for the grasses. The generic accounts have many illustrations (diagrams, chemical formulae, and range maps) and detailed descriptions, with sections on taxonomy and morphology, distribution and habitat, disease problems, disease genesis, clinical signs, pathology, and treatment. Some accounts are incredibly encyclopedic, as 13 pages on Pteridium or 17 on Sorghum. Many genera, as Equisetum, Euonymus, and Sambucus, have keys to species. Some unexpected genera are encountered, as Cannabis, Drosera, and Ginkgo.
This book on North America north of the Tropic of Cancer is, obviously besides for taxonomists, an invaluable, "complete information source for veterinarians, agricultural-extension agents, animal scientists, horticulturalists, botanists, toxicologists, physicians, pharmacists, agronomists, wildlife biologists, farmers, ranchers, and the general public" (back-cover blurb). A more economical CD-ROM should be offered. -- Rudolf Schmid, UC
This is a collection of keys to families and genera of angiosperms that can be encountered in north European gardens. It contains 190 families and 2220 genera of flowering plants, practically almost all that grow or can be grown in temperate regions of the world. The keys and descriptions are taken from much more comprehensive, six-volume work "The European Garden Flora" (for review of its sixth volume see BEN # 269). Main families are illustrated with line drawing plates and most of the illustrations were taken from the 100 Families of Flowering Plants by Hickey & King (2nd edition, Cambridge University Press, 2000). The book is a good reference for identification of temperate families of flowering plants and for identification of many temperate genera. -- Adolf Ceska
A mighty oak has grown from David Frodin's first sapling, Guide to the standard floras of the world (arranged geographically), which was released in August 1964 as a mere 64-page typescript. I proudly keep this next to the 639-page first edition, Guide to standard floras of the world (1984), and now the just published 1124-page edition of the same title--a fine display of evolution in action. Indeed, some in 1964 might have regarded that sapling sappy in view of its competition, Sidney Fay Blake & Alice Cary Atwood's Geographical guide to the floras of the world, part 1 (1942, [[i]], 336 p.), and Blake's part 2 (1961, [[i]], 742 p.), both of which, incidentally, cost me $10.42 in April 1975. However, Frodin's Guide has become a major contribution to botanical bibliography.
This work contains some marvelous mini-essays that can be read in their own right and impressive historical reviews. Coverage is for floras from 1840 through 1999, with some works published in 2000 listed in the five-page addendum.
My only criticisms involve the indices. The massive author index (108 pages) might better have been replaced by a title index because many floras published as continuing series change their authorship or editorship over the decades. In addition, the more useful geographic index (20 pages) would have been better placed after the author index, not before it. The old master was always right on the mark. Frans A. Stafleu's comments (Taxon 34: 558, 1985) about the first edition are still very much apropos: "The detail and the precision of this work are impressive; the author is to be congratulated for this major achievement."
Electronic distribution is planned via EBRARY (http://www.ebrary.com/), as is possibly a CD-ROM. [Modified from Taxon 50: 967-968 (August 2001)] -- Rudolf Schmid, UC
Oregonians north of the Umpqua Divide (roughly Lane Co. and northward) and Washingtonians living betwixt the Pacific Coast and the crest of the Cascades will definitely welcome these revisions of two classic books by Helen Margaret Gilkey (1886-72). She was a professor and herbarium curator at Oregon State University for over 30 years. Her Winter twigs updates a 1962 book whereas her Handbook updates a coauthored 1967 book that in turn was based on various solo-authored predecessor works dating back to 1929. Gilkey's associates did the current revisions.
The new edition of the Handbook rather closely resembles the old. However, revisions were extensive, though mostly subtle, namely: increasing the size of the printed page by about a quarter (from 210x133 to 229x154 mm); including (on p. 6) a list of the 115 treated families indexed to pages (such a list would be much better placed on an endpaper rather than here the banal scale and table of metric, English conversions); numbering of couplets of most of the keys; changing page headers from common names to Latin names of families; reassigning some taxa (e.g., Ribes from Saxifragaceae to Grossulariaceae); updating nomenclature; revising descriptions; adding a few species (no stats are given); and arranging genera and species alphabetically within families, although these are still arranged taxonomically within the pteridophytes (ferns, then non-ferns), gymnosperms, mono-, and dicotyledons. The book has some new line drawings but overall is still sparsely, though adequately illustrated. Significant introductory information on the region covered or its vegetation is still missing.
Those of us raised on William M. Harlow's Fruit key and twig key to trees and shrubs ... of eastern North America (1941, 1946, a combined reissue in 1959) that was used during the dull botanical season will be surprised that the more temperate west has an equally valuable work in the same vein. Gilkey's twig book was nomenclaturally updated and typographically modernized but otherwise is nearly identical to its 1962 predecessor. The Englerian sequence of taxa, the excellent eleven-page introduction, and the artwork, including Gilkey's simple drawings and Packard's 15 fine plates (the revision does not mention Packard for these) are unchanged. The revision has minor textual changes; for example, the key has 80 couplets versus 81 formerly because Sorbus occidentalis and S. sitchensis are now treated as S. sitchensis var. grayi. The book treats 16 families, 35 genera, and 79 mostly native species (including Salix sp.--not the 17 families and 82 species touted on the back cover) and nicely illustrates all but three taxa (Alnus rhombifolia, twigily indistinguishable from A. rubra, and Spiraea betulifolia var. lucida and Symphoricarpos mollis, twigily similar to Sp. densiflora and Sy. albus).
Both books cover the same region and would have benefited from an area map with a few place names (e.g., the Willamette Valley). The distributions given are very generalized. This is especially unfortunate for the twig book. Simply adding British Columbia and California to the appropriate distributions would have provided much information. For instance, for the twig book comparing its 79 species (nomenclature is based on the Oregon Flora Project-- http://www.oregonflora.org/) with those in California (Jepson Flora Project-- http://ucjeps.berkeley.edu/jeps-list.html --the two databases should eventually be compared to show overlap, or lack thereof) reveals a whopping 68 species common to Oregon and California. A corollary of this is that the book unjustly excludes southwestern Oregon (see the Umpqua-Divide statement beginning this review), which also has these 68 species plus probably some of the remaining 11.
These works are usable at all levels from the knowledgeable (i.e., one who can use keys) wildflower, shrub, or tree enthusiast to the professional botanist. Gilkey wrote several other regional floras, which one hopes are in the process of being updated. -- Rudolf Schmid, UC
An essential book for botanical reference libraries. Taxol is "the best-selling anti-cancer drug ever, with world sales of $1.2 billion in 1998"; the book, "from a broader perspective, ... uses taxol as a paradigm to address current issues in the history and sociology of science and medicine" (dust-jacket blurb). Historian Goodman also wrote Tobacco in history: The cultures of dependence (Routledge, London, 1993). -- Rudolf Schmid, UC
Contents: foreword by B. Mathew; intro (by ed.); M. McDonough et al. on Allium; A. W. Meerow on Amaryllid.; P. Sanderson & ed. on Brodiaea alliance; F. Callahan on Calochortus; M. M. Grothaus on Erythronium; D. King on Fritillaria; M. E. Chelednik on se. Iridaceae; E. A. McRae on Lilium; L. Russell on nw. bulb taxa; M. Irish on sw. idem; C. Colston Burrell on e. idem.
An excellent work, very useful taxonomically, because "special attention [was] paid to identifying the distinguishing features of the species" (dust-jacket blurb); with much much information on range, elevation, and and ecology, 101 color photos, 6 B&W line drawings. (See also http://www.nargs.org ) -- Rudolf Schmid, UC
A most informative work, nicely and colorfully done, though rather web-style. -- Rudolf Schmid, UC