The Central Negev Desert and the Arava Valley, two closely situated geographical regions in the southern part of Israel, are areas of extreme desert characteristics. Both are exposed to sporadic, as well as regularly fluctuating environmental condi tions. They differ, however, with respect to the amount of precipitation, average temperature, average relative humidity, number of dew nights and light intensity (Table 1). From Table 1 it is obvious that, although both regions are inhospitable habitats, … Read more... 

The Antarctic botanical zone has been defined as all land south of 60° latitude together with the South Shetland, South Orkney and South Sandwich rslands (Skottsberg 1960, Lindsay 1978). This zone is divided into two regions (Wace 1960, Holgate 1964), the maritime Antarctic region consisting of the west coast the of An tarctic Peninsula and the Antarctic Islands and the continental Antarctic region com prising the east coast of the Antarctic Peninsula and the rest of the Antarctic Continent. The … Read more... 

Nineteen species of Stereocaulon are treated from the northern Andes, mainly from Colombia. Descriptions and keys are given, with notes on the north-Andean distribution and ecology. Seven species are new for the Colombian flora, viz. St. atlanticum, St. claviceps, St. corticatulum (chem. strain with atranorin and perlatolic acid), St. delisei, St. microcarpum, St. pachycephalum and St. pomiferum. St. crambidiocephalum is reported for the first time from Costa Rica, as is St. didymicum from Venezuela, … Read more... 

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