The Ecology of Cailuna vulgaris. 231 
poor in mineral constituents, which probably favours Cailuna , 
whose roots thrive only in very weak nutrient solutions. 
Contejean (4) records Cailuna as typically calciphobe, a view 
endorsed by Bonnier (5) as a result of his investigations on the 
flora of the Carpathians, Alps of Dauphine, etc., but this author 
concludes from a comparison of these districts that, in the case of 
the majority of so-called calciphobe plants, the amount of lime 
present in the soil has only relative significance as a determining 
factor, its importance varying according to other local conditions. 
De Candolle (6) records Cailuna on very poor calcareous soil 
on the Muschel kalk. 
Warming (6) mentions Cailuna as a recorded calciphobe, 
incapable of growing in soils with more than *02—'03% of lime. 
From his own observations he concludes that the plant is very 
accommodating and tenacious of life. “ It can grow on the most 
sterile sand, which may be temporarily dry, or on wet boggy soil 
periodically dry.” 
“ Though capable of growing upon moderately good soil, it 
seldom has the opportunity, because it is expelled by other plants. 
These latter, which are more exacting in their demands, avoid the 
more sterile and acid soil of heaths and resign it to ling.” 
Warming goes on to discuss the influence of lime on vegetation 
in general, and considers that it has been over-estimated. He 
refers to the experimental results of Graebner, who states that 
the significance of lime as a determining factor in the soil, depends 
on the poorness of the latter in other soluble mineral constituents. 
Discussing the vegetative conditions which determine the 
growth of heath plants in North Germany, among which Cailuna 
is mentioned as a typical member, Graebner summarizes his con¬ 
clusions as follows:—“ Ein unbedingtes Erfordernis fur das 
Gedeihen der Heidepflanzen ist das Vorhandensein eines 
nahrstoffarmen Substrates; sobald der Heide oder Heidemoorboden 
gedungt wird, verschwindet die Heidevegetation ganz. Es ist nicht 
nur die auf nahrstoffreicherem Boden den Heidepflanzen in der 
Gestalt der Pflanzenarten mit starkerer Stoffproduction ervvach- 
sende Concurrenz, die Veranderung der Flora bedingt, sondern die 
Heidepflanzen sind auch thatsachlich, wie ich mich durch Cultur 
mehrfach iiberzeugt habe, nicht im Stande grossere Nahrstoff- 
mengen, die fur andere Pflanzen noch gering erscheinen, zu 
verarbeiten.” (7) p. 143. 
