400 NOTES OF A BOTANICAL TOUR 
of six or eight feet, giving shelter to Hymenophyllum Tunbri- 
gense and Acrostichum squamosum, Aspidium fænesecii was 
still plentiful, but most of the other ferns seen lower down 
were now lost. This clouded region corresponds with the 
higher part of the hills and Caldeira in Fayal, being at once 
the region of alpine and of marsh plants; and the lower zone 
of it being also the most productive of Ferns. But the better 
and more comprehensive designation is that of the Region 
of Clouds ; since the absence of cultivation, the green pastu- 
rage, and the prevalence of small marsh and boreal plants, 
interspersed with some of the peculiar alpine productions of 
the Azores, are all apparently attributable to the clouded con- 
dition of the atmosphere. | 
At length the Erica scoparia, that most frequent shrub of 
the Azores, itself yielded before the cloudy atmosphere, and 
we crossed a space of the hill quite destitute of shrubs, but 
covered with a close short herbage, consisting chiefly of 
grasses, Carices and Tormentilla reptans. Here Captain Vidal 
remarked that we had already ascended above the limit of 
the heath. Though I could not dispute the apparent fact, 
yet I felt convinced we were not truly above the natural 
limit of heaths, since the fronds of Pteris aquilina were 
conspicuous around us, rising above the very short pasturage. 
Calluna vulgaris had been observed lower down the Peak; 
and as that heath ascends in Scotland far above the Pteris 
aquilina, 1 read the appearance of the latter as a fair indica- 
tion that we were still within the natural limit of heaths, so 
far as determined by absolute elevation ; but the mist was 
here too dense to allow the sight of any thing beyond a . 
distance of fifty yards. Accordingly in no long time, as we 
gained increased elevation, and aless clouded atmosphere, 
(probably between four and five thousand feet of altitude), 
scattered and very dwarf bushes of Erica scoparia again | 
greeted our eyes, interspersed with a few examples of Daphne 
Laureola and tufts of Aspidium fenesecii, together with occa- 
sional specimens of Lycopodium Selago, whose close and 
upright branches give it a totally different appearance from 
