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siderable moisture in the air, which explains the extraordinary 
tin cans and barbed-wire. It was of interest, therefore, 
by way of contrast to visit places where there was little annual 
rainfall and little moisture in the air. 
Such a place is Ensenada (Guanica Centrale) in the south- 
western part of Porto Rico. The substratum here consists of 
also from the cactus-vegetation, which is found around Guanica 
and above to Laguna Guanica. 
Notwithstanding that the landscape here was dishearteningly 
ry, I succeeded in finding a few aerophilous algae. On the small 
stone bridges in Ensenada (Guanica Centrale) were found on the 
shore pnnanees Gloeocapsa, and Scytonema, which grew also 
on the limestone rocks in the vicinity. Even among the hairs 
on the nace of Tillandsia recurvata I succeeded in finding a 
Gloeocapsa, and on the surface of Cephalocereus Royeni, Chlorella 
and Trentepohlia were found to be comparatively common. 
at least the latter is a typical brackish water genus. But in 
other places pools were found ehh contained water fresh enough 
for a Closterium species to 
On the way to Coamo eile 1 collected a few algae on the 
