The Algal Collection of the US National Herbarium (located in the National Museum of Natural History) consists of approximately 320,500 dried specimens, which, although not exhaustive (no exhaustive collection exists), gives an idea of the order of magnitude of the number of algal species (that number remains unknown).
ðɪ ˈælɡəl kəlˈɛkʃən ʌvðə jˌuːˈɛs nˈæʃənəl hɜːbˈɛɹiəm loʊkˈeɪɾᵻd ɪnðə nˈæʃənəl mjuːzˈiəm ʌv nˈætʃɚɹəl hˈɪstɚɹi kənsˈɪsts ʌv ɐpɹˈɑːksɪmətli θɹˈiːhˈʌndɹɪd twˈɛnti,fˈaɪvhˈʌndɹɪd dɹˈaɪd spˈɛsɪmənz, wˈɪtʃ, ɔːlðˈoʊ nˌɑːt ɛɡzˈɔːstɪv nˈoʊ ɛɡzˈɔːstɪv kəlˈɛkʃən ɛɡzˈɪsts, ɡˈɪvz ɐn aɪdˈiə ʌvðɪ ˈɔːɹdɚɹ ʌv mˈæɡnɪtˌuːd ʌvðə nˈʌmbɚɹ ʌv ˈælɡəl spˈiːsiːz ðæt nˈʌmbɚ ɹᵻmˈeɪnz ʌnnˈoʊn.