IV. DESERT ALGAE, LICHENS, AND FUNGI
167
that among students of desert algae referred to in this paper, Cameron
and Forest usually employ the taxonomy proposed by Drouet, while Bold
and collaborators, Schwabe, the Soviet authors, and the writer of this survey generally adhere to the "classical" nomenclature.
B. DISTRIBUTION
As with most microalgae, the distribution of desert algae is not limited
by geographic barriers. Information recently summarized by Schlichting
(1969) indicates that viable cells of microalgae are present in the atmosphere and are probably carried throughout the world by the wind. To
name one relevant example, Brown, et al. (1964) found viable cells of
the green alga Friedmannia in a Texas air sample. This organism is known
from several desert localities in the Negev Desert of Israel (Chantanachat
and Bold, 1962; R. Ocampo-Paus, unpublished) and in Arizona (R.
Ocampo-Paus, unpublished). It would seem, therefore, that the occurrence
and distribution of desert microalgae depends largely on whether prevailing
ecological conditions are conducive to the growth of the organisms in
question. However, conclusions based on the "ecological" distribution of
desert microalgae are somewhat contradictory. Comprehensive floristic
works are few: Fehér's studies (1936, 1945, 1948), impressive as they
are through the multitude of data and their worldwide scope, are based
on uncertain identifications. Cameron (1960) concludes that filamentous
blue-green and coccoid green algae are predominant in most xeric environments, while coccoid blue-green algae appear with increasing humidity.
But in the arid Negev Desert, Friedmann et al. (1967) found a somewhat
different situation: Unicellular or few-celled green algae (mainly Chlorosphaerales) and filamentous blue-green algae occur in endedaphic,
epedaphic, and hypolithic habitats and also in chasmolithic habitats in calcareous and dolomitic rocks. Coccoid blue-green algae are dominant in
hypolithic growths on flint stones, in chasmolithic habitats in plutonic
rocks, and they seem to inhabit exclusively all endolithic habitats.
According to Cameron (1966, 1969) and Cameron et al. (1970a), the
algal floras of hot deserts and Antarctic xeric, mesophilic, and perhaps
hydrophilic habitats are composed of the same species. The following taxa
(usually used in the sense of the taxonomic principles of Drouet) are
listed:
Green algae: Protoccoccus grevillei (Ag.) Crouan, Protosiphon cinnamomeus (Menegh.) Drouet et Daily, Palmogloea protuberans (Sm.
et Sow.) Kütz., Chlorella vulgaris Beij., Stichococcus subtilis (Kiitz.)
Klerck.
167
that among students of desert algae referred to in this paper, Cameron
and Forest usually employ the taxonomy proposed by Drouet, while Bold
and collaborators, Schwabe, the Soviet authors, and the writer of this survey generally adhere to the "classical" nomenclature.
B. DISTRIBUTION
As with most microalgae, the distribution of desert algae is not limited
by geographic barriers. Information recently summarized by Schlichting
(1969) indicates that viable cells of microalgae are present in the atmosphere and are probably carried throughout the world by the wind. To
name one relevant example, Brown, et al. (1964) found viable cells of
the green alga Friedmannia in a Texas air sample. This organism is known
from several desert localities in the Negev Desert of Israel (Chantanachat
and Bold, 1962; R. Ocampo-Paus, unpublished) and in Arizona (R.
Ocampo-Paus, unpublished). It would seem, therefore, that the occurrence
and distribution of desert microalgae depends largely on whether prevailing
ecological conditions are conducive to the growth of the organisms in
question. However, conclusions based on the "ecological" distribution of
desert microalgae are somewhat contradictory. Comprehensive floristic
works are few: Fehér's studies (1936, 1945, 1948), impressive as they
are through the multitude of data and their worldwide scope, are based
on uncertain identifications. Cameron (1960) concludes that filamentous
blue-green and coccoid green algae are predominant in most xeric environments, while coccoid blue-green algae appear with increasing humidity.
But in the arid Negev Desert, Friedmann et al. (1967) found a somewhat
different situation: Unicellular or few-celled green algae (mainly Chlorosphaerales) and filamentous blue-green algae occur in endedaphic,
epedaphic, and hypolithic habitats and also in chasmolithic habitats in calcareous and dolomitic rocks. Coccoid blue-green algae are dominant in
hypolithic growths on flint stones, in chasmolithic habitats in plutonic
rocks, and they seem to inhabit exclusively all endolithic habitats.
According to Cameron (1966, 1969) and Cameron et al. (1970a), the
algal floras of hot deserts and Antarctic xeric, mesophilic, and perhaps
hydrophilic habitats are composed of the same species. The following taxa
(usually used in the sense of the taxonomic principles of Drouet) are
listed:
Green algae: Protoccoccus grevillei (Ag.) Crouan, Protosiphon cinnamomeus (Menegh.) Drouet et Daily, Palmogloea protuberans (Sm.
et Sow.) Kütz., Chlorella vulgaris Beij., Stichococcus subtilis (Kiitz.)
Klerck.