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it with the idea of a star, as it had previously been given to a con- 
stellation. All are guesses, as no explanation was given by Vaillant, 
who, in 1719, introduced the name. 
The species were previously and indeed subsequently included in 
other groups, Agu7setum and Hippuris especially, now known to 
be very different, but all plants of more or less similar habitat and 
habit. The first mention is by Pliny in his Natural History as an 
Lquisetum ‘* with leaves like a pine”; but the more modern history 
of the genus dates from Caspar Bauhin’s Pixax Theatri Botantct in 
1623, where it is called ‘‘ Hgutsetum foetidum sub aqua repens,” 
and placed between Starganium and Arundo. In the first edition 
of the Genera Plantarum, 1737, Linnaeus places them in the 
Algae between Pilularéa and Fucus; and in the first edition of 
the Speczes Plantarum, 1753, they are so retained, with four 
species, though now between Lichen and ZYremella. In 1478, 
however, Linnaeus transferred them to the flowering plants among 
the Monoecia Monandria, and this view became very prevalent and 
persisted for many years. Most of his immediate successors, how- 
ever, followed his earlier opinion and treated them as cryptogams. 
By Adanson, in 1763, they were included in his family Ara 
(aroids), which comprised such genera as Potamogeton, Isoétes, 
Alga (= Zostera), Callitriche, Myriophylion, Ceratophyllon, 
and Pluvialis (= Natas), between the two last of whic ara 
was placed. In 1789, A. L. de Jussieu put them in the Naiades, 
between Aztpuris and Ceratophyllum; Ventenat, in 1799, in the 
ferns after Hguzsetum. The first author to separate them into a 
family by themselves was Richard, in the botanical account of the 
voyage of Humboldt and Bonpland, 1815, where they were placed 
between Marsileaceae and Piperaceae. Their affinity with the 
Algae has now long been conceded; not universally, however, as 
Lindley and others have placed them with the mosses, while several 
writers have considered them to belong to the vascular cryptogams. 
As a matter of fact they do not approach very close to any other 
group, but probably find their nearest affinity with the Coleochae- 
taceae among the Chlorophyceae, and they should either be made 
the ee order of this group, as is done in Engler and Prantl’s 
diez, or made into a separate subkingdom, as by 
ee He 
The researches which led to a correct understanding of the family 
were carried on by Wallroth, 1815; Waucher, 1821 ; Kaulfuss, 1825 ; 
