172 
ARE SOILS ENRICHED, IMPOVERISHED, [Part III. 
-whose perpetual propinquity is caused by simi¬ 
larity of constitution , or by any of the many other 
causes of propinquity. 
This perpetual propinquity physiologists have 
attributed to the inclination of the plants each 
for the other, instead of both for the soil, or in¬ 
stead of both for the conditions of vegetable life 
existent at the spot: such as, besides those which 
have been alluded to, the degree of drought or 
humidity in the air and in the soil, the freshness 
or the brackishness of the moisture in the soil, 
the degree of light or shade, exposure, &c., &c. 
What is friendship but a name ? And physiolo¬ 
gists have been at the pains to furnish these ve¬ 
getable friends with a name from a dead lan¬ 
guage ( 'plantce sociales ), for fear their living 
disciples should not understand a name from 
their own language. 
Notwithstanding this care, however, Lyell 
actually has mistaken the physiological meaning 
of “ social plants: ” he makes it to be plants of the 
same species which live together in communities , as 
heaths. But it means plants of different species or 
genera which live together in amity , as beech and 
holly. Physiologists even give us the reason of 
their affection; though it is but a cupboard-love, 
that which “expedivit Psittaco suum^aips venter .” 
