THE VEGETATION OF THE JUAN FERNANDEZ ISLANDS 885 



1951) Inga Arvidson showed that in phints of Swedish "alvar" soil leaves are able 

 to absorb sutiticient water from the air (rain, dew and "fog-water") to counterbalance 

 the loss caused by transpiration and that, during a drought, this is quite important. 



With regard to ferns, V. B. Wittrock studied the behaviour of a number of species 

 cultivated in the open (Acta Horti Bergiani I, iSgi) if allowed to dry and then put 

 in a moist chami)er or dipi)cd in water. In some, e. g. Polypodium vulgare and s])ecies 

 of Asplenium, turgescence was restored, while others, e. g. Adiantum capillus Veneris, 

 were killed if allowed to become quite dry, being unable to replace the loss of water 

 through frond absorption. B. Wahlin (Sv. Mosskulturforenrs kvartalsskr., 5, 1943) 

 showed that Polypodium vulgare and Phyllitis scoloperidrium are unable to cover their 

 need of water by root absorption alone and that frond absorption is necessary. In 

 Adianttoii, the cuticle is waxy and no film of water formed. I regret having neglected 

 to study A. chilcnse. 



In the filmy ferns, which appear not to have been studied before, absorption of 

 atmospheric water by the entire, monostromatic frond seems to be quite normal and 

 of paramount importance. 



Chapter IV. 

 The Vegetation. 



Introduction. 



My analysis of the plant communities of Juan Fernandez does not meet the de- 

 mands of modern plant sociology. The use of meter quadrates was not general at 

 the time of our survey, and their serviceableness, quite satisfactory in certain types 

 of plant cover, e. g. in grass-land and heath, is small or none in a dense primeval 

 forest rich in species of ligneous plants and offering all kinds of obstacles. 

 The slopes are mostly steep and very hard-worked, and to get the rare trees 

 and shrubs (which are just as characteristic of a certain type of forest as are 

 the dominants) included would have necessitated a large number of analyses. 

 This our limited time did not permit. Where it was convenient, a square 10 X 10 

 m was selected, a list made of all the species of vascular plants, their rela- 

 tive importance estimated, the stratification observed, and samples taken of the 

 cryptogams, terrestrial and epiphytic. It happened that this procedure was too 

 time-absorbing and that I had to restrict the note-taking to a simple name-list, 

 which, however, will serve to give the reader a general idea of the composition 

 of the vegetation. Rock face communities formed by cryptogams, particularly 

 lichens, are an important feature in Juan Fernandez, where exposed cliffs are 

 met with everywhere; I am no lichenologist, and even if I tried to secure samples 

 of as many species as possible, many must have escaped my attention. The 

 same applies to the synusiae of the ground stratum in forest, scrub and heath, 

 and to the communities of epiphytes. I want the reader to understand that I am 

 quite aware of these deficiencies. 



The nomenclature follows, with regard to the Phanerogams, my paper on 

 the flora (no. 7 in this volume, 1922, and the Supplement, no. 28) and, for the 

 Pteridophytes, Christensen and Skottsberg and (no. i, 1920, no. 28); for the 

 Mosses V. F. Brotherus (no. 8, 1924), for the thallose Hepaticae A. W. Evans 



