THE ROLE OF STUDY OF ALGAE IN THE DEVELOPMENT OF BOTANY

Abstract

LONG BEFORE founding of Botanical Society of America fifty years ago, contributions to various phases of botany had become so numerous that nobody could be familiar with literature of entire field. The end of time when this was no longer possible cannot be stated with certainty but broadly speaking it may be said to have ended with death of Sachs, a man who has been called the last of great epitomists. In this age of specialization we have reached a point where it is becoming more and more difficult for a man to cover literature past and present even in his own specialty. Thus outside of their own special field of interest many botanists have only a scanty knowledge of contributions from other fields of botany that have advanced botanical science as a whole. In this review of progress in study of algae emphasis will be placed on those contributions that are general botanical significance instead of on those that are of interest only to phycologists. Until early in nineteenth century practically all contributions to botany were in field of taxonomy. Linnaeus' Species plantarum (1753), official starting point for nomenclature of plants, places 14 of recognized genera among order algae. Today, only four of these genera (Coniferva, Ulva, Fucus, and Chara) are considered algal in nature. Within a few decades after publication of Species plantcarum botanists who were specialists on algae appeared on scene. In their floristic studies of algae of various regions they soon realized that there were species additional to those described by Linnaeus. They described new species that they discovered but placed them in one of four algal genera recognized by Linnaeus. This practice was continued even when hundreds of species had been added to Linnaean genera. Examples of this are to be seen in Dillwyn's (1802-1809) British Confervae and in Turner's (1808-1819) four-volume treatise entitled Fuci. Early in nineteenth century phycologists began to have temerity to describe genera additional to sacred four recognized by Linnaeus. New genera appeared in literature at a rapid rate and many of earlier established genera were divided ipto two or more genera. With establishment of a number of genera there came grouping of them into taxa of higher categories. Lamoroux (1813) was first to do this. He placed marine algae in a he called Thalassiophytes and divided this family into six 4orders, three most important being Fucacees, Floridees and Ulvacees. Distinctions between these taxa were made in part, but not exclusively, upon color. The next significant grouping into major taxa was proposed by Harvey (1836, 1841) when he divided algae into four (Melanospermeae, Rhodospermeae, Chlorospermeae, Diatomaceae), each with a number of families. Distinction between fiist three was made on basis of their brown, red, or green color. This distinction on basis of color has stood test of time and has been found to be correlated with distinctive types of reproductive structure. The names Harvey applied his maj or taxa were soon supplanted by other names, Melanospermeae being called Phaeophyceae, Rhodospermeae called Rhodophyceae, and Chlorospermeae called Chlorophyceae. Harvey's Diatomaceae included both desmids and diatoms but it was soon realized that desmids belonged among Chlorophyceae. The major taxon variously called Chlorospermeae or Chlorophyceae also included blue-green algae. These were first segregated by Stizenberger (1860) in a separate taxon, that he called Myxophyceae. Somewhat later Luther (1899), primarily on basis of flagellation of motile reproductive cells, segregated certain of supposedly grass-green algae into a class that he called Heterokonteae (Xanthophyceae). Until beginning of present century flagellates with chromatophores of various colors were considered protozoa and almost all of our knowledge concerning them was due to efforts of protozoologists. An exception must be made in case of Cilamydomonas-Volvox series. For nearly a century botanists have placed this series among Chlorophyceae. Beginning more than three quarters of a century ago botanists were in general agreement that Chlorophyceae have arisen from a unicellular flagellated organism of chlamydomonad type. Many also thought that flagellated reproductive cells of Phaeophyceae indicate that they have arisen from a unicellular flagellated ancestor. Correlated with this was gradual appearance of view that flagellates related to unquestionable algae should be placed among algae instead of being placed among protozoa. Although not pioneer in this idea Pascher was chief advocate of it and discoverer of many new algae obviously related to pigmented flagellates. For some time certain botanists had held that dinoflagellates should be considered algae. Their argument was based on discovery of certain unicellular free-floating and sessile forms whose life cycle involved a formation of motile cells of a gymnodinoid nature. These botanists held that immobile phase is. comparable to that of unicellular coccoid Chlorophyceae and that motile phase is zoosporic in nature. Many protozoologists held that the. swarmers are dinoflagellates and that coc-