n. III. OR POISONED BY VEGETABLE GROWTH? 149 



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 physiologists 

 have been at the pains to furnish these vegetable 

 friends with a name from a dead language (plantce 

 sociales)^ for fear their living disciples should not 

 understand a name from their own language. 



l!^otwithstanding this care, however, Lyell actually 

 has mistaken the pysiological 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 diflerent species or genera which live 

 together in amity ^ as beech and holly. Physiologists 

 even give us the reason of their aflfection ; though it is 

 but a cupboard-love, that which ' expedivit Psittaco 

 suum ;^aips venter.' 



In reference to this, Eichard writes : — ' This 

 unctuous matter was the product of a kind of excretion 

 performed by the roots. To this matter, which, as we 

 have said, is different in different species of plants, the 

 sympathies and antipathies which certain plants have 

 towards each other have been attributed. It is well 

 known, in fact, that certain plants have, as it were, a 

 kind of liking to each other, and constantly live 

 together. These are named social plants.' 



And again : ' Eoots also excrete, by their slender 

 extremities, certain fluids, which are injurious or useful 



