Linne's contribution to algology was not as profound as to botany and several of his algal descriptions remain difficult to interpret in a modern context - let apart the identification of his algal types. One of them is Ulva latissima, originally described from the town of Marstrand on the Swedish west coast.

At that time, Linne did not use binomials and the new species was described in his 'Iter Vaestgoeta Resa 1746' ('it. W:goth.') as: 'ULVA oblonga plana und[ul]ata membranacea viridis. Fucus longissimo latissimo, tenuique folio. Bauh. prodr. 154.'. The text that follows can be translated to: '[She] grew right much on the bottom of the sea, laying there full of mud, looking as dark waves, so that she could not be well identified, before she was washed carefully. She was abundant on the sea bottom, and she did bends and twists, in and under of which numerous sea animals, such as Asteriae, Medusae, Gamari, found comfortably shelter. This [species] has not in the past been recorded in the registers of Flora Svecicae.'.

This account appears just after Linne's description of another marine alga from Marstrand, namely of: 'Fucus caule tereti brevissimo, folio maximo oblongo indiviso (Flor. 1010).' The text that follows here reads: '[He] covered entirely the sea bottom at the jetty of Marstrand; [he] looked like a thin layer of leather, oval to elongate, usually two ells long and 1 ell broad, forming waves. At the base, [he] was narrow or had a short petiole; [his] root adhered to stones with finger-like organs.'.

In 1753, Linne formally described both, the former as Ulva latissima and the latter as Fucus saccharinus (Laminaria saccharina), citing his 'It. w:goth.' (as only reference in the protologue of U. latissima). In Fl.Sv.2nd.ed. (1755, pp. 432, 433), the two taxa remain clearly delineated and the reference to 'It. w:goth.' is maintained. The confusion occurred later and the exact reason cannot be known, but comparing Linne's later accounts of Ulva latissima, it can be noted that in Syst.Nat.12th ed. (1767, p. 719) Linne excludes the reference to 'It.w:goth' adding a sentence that relates Ulva latissima to Musae (i.e. Alaria). In a commentary in Mant.alt. (1771, p. 508), Ulva latissima is 'grouped' with Fucus esculentus (Alaria esculenata), the two said to be distinguished from Fucus saccharinus which lacks a midrib. This last observation indicates clearly that 'Ulva latissima' was now accepted as an Alaria species - which is certainly erroneous because Alaria does not grow in Marstrand or elsewhere on the Swedish west coast. Hudson (Fl.angl. 1778, p. 567) reacted to Linne's new concept creating Ulva fusca to encompass the 'new alga' citing U. latissima as a potential synonym. Turner (Fuci. 1811, p. 69-72), who studied the Linne herbarium reported that Ulva latissima was a bullate form of Fucus saccharinus - an opinion accepted by Lyngbye (Tent.Hydr.Dan.1819, p. 22) and Wahlenberg (Fl.Lapp.1812, p. 494), but certainly not the majority who continued to treate U. latissima as a species of Ulva (e.g. De Candolle in Lamarck & De Candolle Fl.Fr.ed.2.1805; Agardh Syn.1817, Sp.Alg.1823; Harvey Phyc.Brit. 1848, tab.171; Areschoug Phyc.Scand.Mar.1850; Thuret in M?m.soc.imp.sci.nat. Cherbourg 2. 1854; Hauck Die Meeresalg. 1884, p. 437; Newton Br.Seaw.1931, p. 78.; Levring Algenfl.norw.Westk. 1937, p.18.; Kylin Chlor.schwed.Westk.1949, p. 17).

While Turner's observation might be correct, there are reasons to question the authenticity of the 'type'. There is no Laminaria element in the protologue (or later accounts) of Ulva latissima - Linne himself having later associated this species with Alaria and not Laminaria. Accepting (or not) the hypothesis that a confusion of the Marstrand collections occurred after 1755 - and this would not be the only case with Linne's herbarium types (cf. Fucus spiralis L., Fucus furcellatus L., and Fucus rubens L.) - Ulva latissima has to be in agreement with the protologue (i.e. a Marstrand, green, membraneous-oblongate alga...). The only allien element in the protologue of Ulva latissima is the reference to Fucus longissimo latissimo tenuique folio. Bauhin prodr.154. This is probably the (only) reason that Linne later associated U. latissima with Alaria, but, since this genus does not grow on the Swedish coast, the Bauhin element must be excluded as an error - later corrected by Linne who cited this reference under the protologue of F. esculentus L.

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