189().] ESSAYS. 113 



in woods or from a heath, is chosen for the culture of Heaths and 

 Rhododendrons. But it is not every kind of forest or heath mould 

 that can be made use of. When earth of that nature has been quite 

 dry for a long time it is no longer fit for this purpose. It is known 

 that such plants should be transplanted from their forest home with 

 the soil still clinging to the roots ; the roots should not be exposed 

 and should be cut as little as possible. By drying the soil the 

 mycelium is killed ; by shaking off the soil, or by trimming the roots, 

 the mycelium is removed. 



The failure of all attempts to propagate the oak, beech, heath, 

 rhododendron, wintergreen, broom, or spurge laurel, by slips or 

 cuttings set in pure sand, is explained in the same way. Roses, ivy 

 and pinks, the roots of which possess no mycelial mantle, are easily 

 grown from slips in pure sand. But though the cuttings of oak, etc., 

 strike root, they do not progress in their development, because the 

 superficial cells of their rootlets have not the power. of absorbing food 

 when not associated with a mycelium. It is only when the slips are 

 put into sand having a liberal mixture of fresh leaf or heath mould, 

 that any plants can be reared. Various experiments are reported 

 which all confirm the theory that the fungus mycelium is not only 

 useful but necessary to the growth of many flowering plants. 



In return for its important services, the fungus undoubtedly receives 

 a full equivalent, in the form of substances helpful to its growth 

 which have been formed by the sunlight in the green leaves. 



The range of species which live in a social union such as is here 

 described is certainly very large. Besides many shrubby plants of 

 the heath, arbutus and wintergreen families and the rhododendrons 

 and daphnes, there are a large number of the conifers and apparently 

 all the cupulifera?, as well as several willows and poplars which are 

 dependent for nutrition on the assistance of mycelia. 



The green- leaved plants which are forced to be partners in this 

 strange alliance are notably of gregarious growth, and cover whole 

 tracts of country, forming boundless heaths, as in many parts of the 

 British Isles, and measureless forests everywhere, as of oak, beech, 

 fir, and poplar." 



A very curious alliance exists between the Monotropa, the common 

 Indian Pipe of moist woods, and a fungus mycelium. The Indian 

 Pipe has no roots of its own, and absorbs all its nourishment from 

 the cells of a mycelium. But the Indian Pipe has no chlorophj^ll, 

 and so far as we yet know, gives back nothing to the fungus which 

 helps it to live. A partnership with all the advantages on one side, 



