Linnaeus's "sexual system" (Linnaeus, 1754) [51] in which he grouped plants according to the number of stamens and carpels in their flowers, although wholly artificial was advantageous in that a newly discovered plant could be fitted in amongst those already known. He divided the plant kingdom into 25 classes, one of which was the Cryptogamia — plants with "concealed reproductive organs" (see above) (Smith, 1955).[5] Linnaeus accepted 14 genera of algae of which only four, Conferva, Ulva, Fucus and Chara, contained organisms now regarded as algae (Dixon, 1973 p. 231).[52] As a consequence of the great increase in the number of species the artificiality of the Linnaean system was appreciated so that during the 18th Century and early 19th Century considerable numbers of new genera were described. J.V.F.Lamouroux in 1813 [53] was the first to separate the groups on the basis of colour, however this was not taken up by other botanists and it was Harvey who, in 1836, divided the algae into four major divisions solely on the basis of their pigmentation: Rhodospermae (red algae), Melanospermae (brown algae), Chlorospermae (green algae) and Diatomaceae (Dixon,1973 p. 232).[52]