166
E. IMRE FRIEDMANN AND MARGALITH GALUN
I. Desert Algae
A. INTRODUCTION
In deserts, algae occur in both aquatic and nonaquatic localities. The
nonaquatic (xeric) algal habitats are characteristic of deserts, and their
inhabitants may properly be considered "desert algae." Some of these are
free-living (i.e., nonlichenized) forms, while others occur as lichen phycobionts. This chapter deals with the nonaquatic, free-living, desert algae,
and the lichenized forms are only occasionally mentioned.
Any attempt to compile a general account of desert algal flora runs into
difficulties because, at the present time, no consensus exists regarding the
basic principles of taxonomy of green and blue-green microalgae. A short
explanation of these circumstances may be helpful in understanding the
often confusing discrepancies in published data.
In Myxophyceae, species descriptions were brought into synthesis in the
monumental book of Geitler (1932). This was followed by several comprehensive works, the latest of which is Starmach's (1966) flora. In recent
years, efforts have been made to improve the purely morphological approach of the "classical" system by searching for species characteristics
based on numerical taxonomy, microbiological methods, and on pure cultures of the organisms. An entirely different approach was suggested by
Drouet and Daily (1956) and Drouet (1968). By reducing the number
of specific and generic taxa, they relegated literally hundreds of "classical"
species to synonyms. Whitton (1969), writing about the "present chaotic
stage of blue-green algal classification" recommends that, until a new
Myxophycean taxonomy can be established, the classical nomenclature
should be used for practical purposes as a workable though admittedly
artificial system.
As for green microalgae, taxonomic identifications in earlier floristic
works are more often than not unreliable. Starr (1955) and Bold (1970)
and his followers, working with pure cultures, established a number of new
genera and species based on biochemical and sophisticated morphological
characteristics. In contrast, Drouet and Daily (1956), stressed the importance of herbarium material and united a number of coccoid green microalgal species in taxa which are not used by the followers of Bold:
Protococcus grevillei (Ag.) Crouan, Palmogloea protuberans (Sm. et Sow.)
Kiitz, Phytoconis botryoides (L.) Bory, and Protosiphon cinnamomeus
(Menegh.) Drouet.
As a result of these differences, floristic data of authors using different
and conflicting nomenclatures are often not comparable. It may be noted
E. IMRE FRIEDMANN AND MARGALITH GALUN
I. Desert Algae
A. INTRODUCTION
In deserts, algae occur in both aquatic and nonaquatic localities. The
nonaquatic (xeric) algal habitats are characteristic of deserts, and their
inhabitants may properly be considered "desert algae." Some of these are
free-living (i.e., nonlichenized) forms, while others occur as lichen phycobionts. This chapter deals with the nonaquatic, free-living, desert algae,
and the lichenized forms are only occasionally mentioned.
Any attempt to compile a general account of desert algal flora runs into
difficulties because, at the present time, no consensus exists regarding the
basic principles of taxonomy of green and blue-green microalgae. A short
explanation of these circumstances may be helpful in understanding the
often confusing discrepancies in published data.
In Myxophyceae, species descriptions were brought into synthesis in the
monumental book of Geitler (1932). This was followed by several comprehensive works, the latest of which is Starmach's (1966) flora. In recent
years, efforts have been made to improve the purely morphological approach of the "classical" system by searching for species characteristics
based on numerical taxonomy, microbiological methods, and on pure cultures of the organisms. An entirely different approach was suggested by
Drouet and Daily (1956) and Drouet (1968). By reducing the number
of specific and generic taxa, they relegated literally hundreds of "classical"
species to synonyms. Whitton (1969), writing about the "present chaotic
stage of blue-green algal classification" recommends that, until a new
Myxophycean taxonomy can be established, the classical nomenclature
should be used for practical purposes as a workable though admittedly
artificial system.
As for green microalgae, taxonomic identifications in earlier floristic
works are more often than not unreliable. Starr (1955) and Bold (1970)
and his followers, working with pure cultures, established a number of new
genera and species based on biochemical and sophisticated morphological
characteristics. In contrast, Drouet and Daily (1956), stressed the importance of herbarium material and united a number of coccoid green microalgal species in taxa which are not used by the followers of Bold:
Protococcus grevillei (Ag.) Crouan, Palmogloea protuberans (Sm. et Sow.)
Kiitz, Phytoconis botryoides (L.) Bory, and Protosiphon cinnamomeus
(Menegh.) Drouet.
As a result of these differences, floristic data of authors using different
and conflicting nomenclatures are often not comparable. It may be noted