THE AZORES 



381 



dwarfed forms of the species of Isoetes and Littorella above named ; 

 the latter formed almost a turf. 



The Lagoa Rosada, or the Rosy Lake, is situated in the middle of 

 the island between Ribeiras and Praynha do Norte and near the 

 Caldeira de Santa Barbara, indicated in the chart. Elevated about 

 2950 feet above the sea, it occupies the bottom of a broad basin, 

 which may possibly be of crateral origin, and it is the only one of 

 the large mountain lakes that could be so regarded. It is oval in 

 shape, and is between 200 and 250 yards long, and from 100 to 150 

 yards broad. Viewed from the slopes above in the late afternoon, 

 its waters had a beautiful inky-blue hue, so that " Lagoa Ccerulea " 

 seemed a more appropriate name. Besides Potamogeton polygoni- 

 folias, the two forms of Isoetes azorica and Littorella lacustris here 

 thrived. 



Lying close together in a level district on the top of the mountains 

 behind Santo Amaro, and elevated between 2800 and 2900 feet above 

 the sea, are the Lagoa do Ilheo (Lake of the Isles) and the Lagoa 

 Negra, or the Black Lake. The Lake of the Isles is about the size 

 of the Caiado Lake, if not larger. It contains two islands, and is 

 half-covered by the Potamogeton so common in these mountain 

 lakes; whilst a tall form of Scirpus palustris, two feet in height, is 

 not uncommon in the shallows. The Lagoa Negra is about 300 

 yards in length and oval in shape. Here were to be seen the species 

 of Potamogeton, Littorella, and Isoetes above named. 



A number of small, circular, shallow lakelets, twenty-five to fifty 

 yards across, fill the bottom of the craters of the numerous small cones 

 dotted about this elevated lake region. Occasionally in midsummer 

 they are almost dried up, when the still moist muddy surface may be 

 covered by a turf of Scirpas fluitans, which doubtless resumes its 

 usual aquatic habit when the lakelet refills in the rainy season. 

 More often they are appropriated by the ubiquitous Potamogeton 

 polygonifolius, or, when the surface is clear, plants of Isoetes azorica 

 and Littorella lacustris in their two forms thrive in their waters and 

 at their borders. It may be here added that almost all the aquatic 

 and sub-aquatic plants previously mentioned in connection with 

 the island of Pico flourish in one or other of the numerous small 

 crater lakes of the island, Sphagnum often growing at their borders. 



In the vegetation around the large lakes of this region one can 

 sometimes recognise a succession of formations. Whilst the Potamo- 

 geton before named occupies the shallows, Scirpus -fluitans monopo- 

 lises the soppy ground at the lake's border, and outside this is a 

 broad belt of Sphagnum, where Scirpus multicaulis, Car ex flava, 

 Anagallis tenella, and Hydrocotyle vulgaris thrive. 



With regard to the occurrence of Littorella lacustris and Isoetes 

 azorica in this region of the mountain lakes, some further remarks 

 may here be made. Both display two forms, a dwarfed form on 

 the exposed mud-flats, and a large form with long cylindrical leaves 

 growing in the deeper water, as in the case of Isoetes, or where the 

 water just covers the ooze at the lake's margin, as with Littorella. 

 Whilst the dwarfed plants of Littorella lacustris were well in flower 

 at the end of July, the large plants were only showing the flower- 



