THE ECONOMY OF NATURE 5 



now known in other groups of plants, though it was first discovered 

 in the lichens. According to the Encyclopedia Britannica, 



" Lichens are frequently found in the most exposed and arid situations. 

 In the extreme polar regions these plants are practically the only vege- 

 table forms of life and possess the capacity of resisting extremes of warmth, 

 cold and drought without destruction. On a bare rocky surface a fungus 

 would die for want of organic substances, and an alga from drought and 

 want of mineral substances. The lichen, however, is able to grow as 

 the alga supplies organic food material, and the fungus has developed a 

 battery of acids which enable it actually to dissolve the most resistant 

 rocks." (Pioneer work !) 



The lichens are characterised by their slow growth, which is 

 associated with great length of life. It is possible, says Dr. O. V. 

 Darbishire, that specimens of such long-lived species of Lecidea 

 geographica actually outrival in longevity the oldest trees. 



From this we may see that Nature does know a method of 

 production and of advance superior to our usual methods of 

 Domestication, which aim at exploitation rather than counter- 

 service. Symbiosis entails the fullest physiological and biological 

 " Give and take." It thus brings about a summation and again, 

 rather than a loss, of factors. Symbiosis enriches the protoplasm. 

 Domestication impoverishes it. 



Bougie*, a French sociologist, say- : 



"la mise en commun des forces individuelles engendre une force totale 

 plus grande que leur somme, ... la combinaison des travaux 

 augmente leur efncaciteV' 



and this also applies in Nature. Here as there, the more A can 

 rely on B, the more A can give and in turn stimulate B to increas- 

 ing outputs. Further, the more A and B progress in correlated 

 efficiency, the better will they be able to help C and D, as fellow- 

 members in evolution, causing them, in turn, to increase in 

 efficiency and usefulness. The whole level of life is thus gradually 

 and almost insensibly advanced by every symbiotic increase of 

 power. 



What we have shown in detail in the case of the fungus and the 

 alga is parallelled by the relation between insects and plants, 

 except that in the latter we have a more developed, i.e., " un- 

 attached " form of Symbiosis, whilst " attached " Symbiosis is 

 peculiar to the lichen and a few other compound forms. Grant 

 Allen long ago pointed out that the insect has turned the whole 

 surface of the earth into a boundless flower-garden, which 

 supplies it from year to year with pollen or honey, and the plant 



