116 ^ CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



begins with Linnaeus' (1753) Species pl<intarum. It is of interest to note that 

 in Linnaeus' system the algae were grouped along with the pteridophytes, mosses, 

 and fungi in a single class, the Cryptogamia, whereas the phanerogams were 

 divided into 23 classes. Linnaeus recognized 14 genera of algae but only four 

 of them {Conferva, TJlva, Fucus, and Char a) comprised algae in the current 

 sense and two others {Byssus and Tremella) included a few species of algae. 

 During the following fifty years botanists were content to accept the classifi- 

 cation of Linnaeus and, with very few exceptions, always referred their algal 

 species to his genera. Usually, Conferva received the filamentous, TJlva the mem- 

 branous, and Fucus the fleshy forms, and treatises were written on the largest 

 of these three genera, namely, Fucus and Conferva (e.g., by Gmelin, 1768; Es- 

 per, 1797-1808; Dillwyn, 1802-1809; Vaucher, 1803; Lamouroux, 1805; Turner, 

 1808-1819). Chara was frequently excluded from the algae. 



Stackhouse was the first to break away completely from the custom of recog- 

 nizing only the Linnean genera of algae. He concerned himself especially with 

 the British species of the marine genus Fucus, and his study of them brought him 

 to the realization that this comprehensive genus comprised a large number of 

 distinct taxa which he accordingly removed to new genera. In a series of three 

 works (1795-1801, 1809, 1816) he divided Fucus into 67 genera (including one, 

 Pygmaea, now known to be a lichen). Papenfuss (1950a) has typified Stack- 

 house's genera and has discussed their fate. 



In 1813 Lamouroux published his Essai sur les genres de la famiUe des thaJ- 

 lasssiopJiytes non articulees, which formed an important advance in that he, 

 in addition to establishing a number of new genera, mostly as segregates from 

 Fucus, proposed a system of classification of the algae into major taxa (orders) 

 based in part on color. 



C. Agardh (1817, 1824) and especially Harvey (1836) made significant 

 modifications in Lamouroux' system. Harvey divided the algae with which he 

 was concerned into the four divisions (phyla) Melanospermeae (brown algae), 

 Rhodospermeae (red algae), Chlorospermeae (green algae), and Diatomaceae 

 (diatoms and desmids). Without realizing it, Lamouroux and Harvey thus in- 

 troduced a biochemical character into the classification of the algae. Subse- 

 quent investigations have firmly established the soundness of this character as 

 an indicator of phylogenetic afiinit}^ On the basis of pigment composition and 

 other characters of seemingly comparable merit several major taxa, in addition 

 to Harvey's original four, have now been recognized. In the present treatment 

 the assemblage is considered as comprised of seven phyla and in addition three 

 classes, one of which, the Schizophyceae (bluegreen algae), is regarded as con- 

 stituting along with the class Schizomyceteae (bacteria) the phylum Schizo- 

 phyta, and two of which are composed of forms of uncertain affinity. The his- 

 tory of these major groups is reviewed in the separate sections into which the 

 body of this chapter is divided. 



In 1836, Endlicher divided plants into two kingdoms — Thallophyta and Cor- 

 mophyta. The designation Thallophyta was later used as a phyletic name for 

 all plants below the level of the Bryophyta. Although the term still has merit 

 as denoting plants of a certain morphological type, it is now generally recog- 

 nized that the various classes of algae and fungi can no longer be regarded as 

 belonging to a single phylum. 



