The Equisetum Species (Horsetails) of the British Isles

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L. Watson and M. J. Dallwitz

Character List

#1. <Common name:>/

#2. <Synonyms:>/

#3. The rhizomes <description>/

#4. The rhizomes <whether tuberous>/

1. bearing tubers/

2. not tuberous/

The data on rhizomes are mainly quoted from Goebel (1887), who referred to Duval-Jouve, and need checking. Since the available illustrations of E. sylvaticum show non-tuberous rhizomes, the species is scored here as variable.

#5. The shoots <dimorphism>/

1. conspicuously dimorphic: the cone-bearing stems thick, unbranched, brown and non-assimilating, appearing in early spring and withering before the emergence of the sterile, branched, green, persistent ones/

2. distinguishable as fertile and sterile: both types produced at the same time, but those bearing cones remaining non-green and unbranched until after spore dispersal, and only later becoming green and branching so as to resemble the sterile stems vegetatively/

3. all green and alike vegetatively, the sterile and cone-bearing shoots emerging at the same time/

#6. The brown, non-assimilating fertile stems <height>/

cm high/

#7. The brown, non-assimilating fertile stems <internode diameter>/

mm in diameter/

#8. The brown, non-assimilating fertile stems <number of sheaths>/

1. with numerous sheaths and relatively short internodes/

2. with only 4 to 6 relatively distant sheaths/

#9. The sheaths <of the brown fertile stems, number of teeth>/

toothed/

#10. The main stems <of the assimilating shoots, height>/

cm high/

#11. The main stems <of the assimilating shoots, diameter of internodes>/

mm in diameter/

#12. The main stems <of the assimilating shoots, carriage>/

1. erect/

2. decumbent/

#13. The main stems <of the assimilating shoots, colour>/

1. bright green/

2. dull green/

#14. The main stems <of the assimilating shoots, rough or smooth>/

1. very rough/

2. slightly rough/

3. smooth/

#15. The main stems <of the assimilating shoots, branching>/

1. bearing whorls of slender branches at the nodes/

2. sparingly branched, the branches solitary and similar to the main stem/

3. simple <unbranched>/

#16. The main stems <of the assimilating shoots, persistence>/

1. persisting through the winter/

2. dying down in autumn/

#17. The main stem internodes <of the assimilating shoots, whether swollen>/

1. somewhat swollen/

2. not swollen/

#18. The main stem internodes <of the assimilating shoots, number of longitudinal grooves>/

grooved/

#19. The <longitudinal internodal> grooves <in the main stem internodes of the assimilating shoots, details>/

1. fine, the ribs between them not prominent/

2. deep, with prominent ridges between/

#20. The main stem internodes <of the assimilating shoots, presence of a central hollow>/

1. solid/

2. with a central hollow/

#21. Central hollow <of the main stem internodes of assimilating shoots, relative diameter>/

1. much less than half the diameter of the internode/

2. about half the diameter of the internode/

3. more than half the diameter of the internode/

#22. Endodermis <in main stem internodes of assimilating shoots, location>/

1. surrounding the individual vascular bundles/

2. comprising a single layer outside the ring of vascular bundles/

3. comprising two layers, one outside and the other inside the ring of vascular bundles/

#23. The main stem sheaths <of assimilating shoots, colour>/

#24. The main stem sheaths <of assimilating shoots, length relative to breadth>/

1. about as broad as long/

2. longer than broad/

#25. The main stem sheaths <of assimilating shoots, loose or appressed>/

1. loose/

2. appressed/

#26. The main stem sheaths <of assimilating shoots, numbers of teeth>/

toothed/

#27. The teeth <of the main stem sheaths of assimilating shoots, ribbing>/

1. ribbed/

2. not ribbed/

#28. The teeth <of the main stem sheaths of assimilating shoots, details>/

#29. The teeth <of the main stem sheaths of assimilating shoots, persistence>/

1. persistent/

2. caducous/

#30. The primary branching <regularity>/

1. symmetrical/

2. asymmetrical/

#31. The primary branches <when present, few or many>/

1. few/

2. numerous/

#32. The primary branches <carriage>/

1. ascending/

2. spreading/

3. drooping/

#33. The primary branches <of assimilating shoots, whether themselves branched>/

1. simple/

2. secondarily branched/

#34. The primary branch internodes <of assimilating shoots, number of angles>/

-angled/

#35. The primary branch internodes <of assimilating shoots, number of grooves>/

grooved/

#36. The primary branch sheaths <of assimilating shoots, number of teeth>/

toothed/

#37. The first <primary> branch internodes <of assimilating shoots, relative length>/

1. much shorter than the subtending sheaths/

2. at least as long as the subtending sheaths, at least on the upper parts of the stem/

#38. The primary branch internodes <of assimilating shoots, solid or hollow>/

1. solid/

2. hollow/

#39. Stomata <of assimilating shoots, insertion relative to the adjacent epidermal cells. See Notes>/

1. sunken <i.e., relative to the adjacent epidermal cells>/

2. not sunken <i.e., relative to the adjacent epidermal cells>/

The accounts to hand (see References) give no information on the distribution of stomata, nor do they specify the organs observed. According to Matus, the main stems of the assimilating shoots of E. telmateia (traditionally described as whitish) lack both chlorenchyma and stomata, so stomatal information for that species at least presumably represents the (green) branch internodes and/or sheaths. There is no reason to assume that stomatal configurations from different parts of a plant will be the same, and if flora descriptions do not reflect properly comparative observations, the data are unreliable.

#40. The cones <length>/

cm long/

#41. The cones <blunt or apiculate>/

1. blunt/

2. apiculate/

#42. Spores <whether fertile>/

1. fertile <implicit>/

2. abortive/

#43. Spores released <months released>/

1. April/

2. May/

3. June/

4. July/

5. August/

6. September/

Comments

#44. <General comments:>/

Distribution

#45. <Distribution in the British Isles>/

Classification

#46. Subgenus/

1. Equisetum/

2. Hippochaete <= Sclerocaulon>/

#47. Section <of subgenus Equisetum>/

1. Aestivalia/

2. Subvernalia/

3. Vernalia/

#48. = <Hybrid origin>/


To view the illustrations with detailed captions, go to the interactive key. This also offers full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2004 onwards. The Equisetum species (horsetails) of the British Isles. Version: 7th March 2015. http://delta-intkey.com’.

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