"You can browse though the hierarchy by clicking on the names below and drilling down. At each level the numbers of current species are given for each taxon. Only currently accepted names are currently included. Should you find any errors, please click on the little envelope icon, and you can send me an e-mail via the site. In order to make calculations of the numbers of species of living algae, note that 68 or so species of flowering plants (seagrasses) are included for the present (under the Phylum Magnoliophyta), and about 2000 fossil algae, mainly calcium- and silica- secreting forms. A few fungal names are included. We are currently revising the classification to take account of some recent phylogenetic studies; however, because of difficulties with the Botanical and Zoological Codes, this may seem very inconsistent in places.
Plants vs Animals
The age-old question of what is an animal and what is a plant creates classification problems for botanists and zoologists alike, and in many groups the differences are quite unclear. The classification of organisms currently included in AlgaeBase adopted here closely follows a draft classification by Dennis Gordon (Principal Scientist, Aquatic Biodiversity & Biosecurity, National Institute of Water & Atmospheric Research, Wellington, New Zealand) and colleagues (including AlgaeBase) in July 2011, with the exception of the euglenoid flagellates and the dinoflagellates for which AlgaeBase has mostly retained the ICBN (botanical) suffixes; however, we have occasionally added the equivalent taxa in zoology. We have largely adopted this classification for the sake of conformity.
For the marine flowering plants we follow Angiosperm Phylogeny Group III system in respect of the Angiosperms in which all seagrasses are in one order, the Alismatales. The family Cymodoceaceae is not recognised currently in this system, but we have retained it for the present. The seagrasses are, of course, not algae, but are included here for convenience."