Many years ago I received a consignment of _Pinus cembra_, the Arolla pine, which is the common growth of the Alps. The trees arrived late in the afternoon, and we unpacked them at once, for the days were at their shortest, and I was eager to get them all planted—there were a dozen or more—before nightfall. To my dismay I found that the roots were all covered with a network of grey film, the mycelium, as the learned would call it, of some fungus. My gardener and I were not a little indignant with the nurseryman who sent out the plants in so filthy a condition. We sent for a bucket of water and washed clean as many of the trees as we could; mercifully there was not daylight enough left to purge them all of their dirt. To our amazement, the trees which we washed soon began to show signs of sickness; they dwindled for three or four years and looked as if they must die; slowly, very slowly, the invalids recovered. Their unwashed mates never flinched for a moment, made roots gaily, and took quite rapidly to their new home. The puzzle was great, until a few years later I received Kerner’s great book, “The Natural History of Plants,” and then the mystery was cleared up. The sorrows of the washed trees were those of the planters of the West Indian Islands. Like Mr. Wilberforce, we had deprived them of their slaves. Luckily, the humus of the plantation in which they were placed must have contained the spores necessary to the formation of the fungoid growth, otherwise they would doubtless have died. Kerner’s chapter on the _Symbiosis_, or social union of plants, is curiously interesting. He gives a list of flowering trees and plants which are absolutely dependent upon what he called the mycelial mantle with which fungi cover their roots for the absorption of their daily food. Limes, roses, ivy, pinks may be propagated by cuttings which will root in pure sand. No such method is possible in the case of the oak, the beech, firs, broom, rhododendron, and a host of others, which demand an admixture of soil containing a proportion of mycelia, without which they are unable to feed themselves; and so, like babies, with neither breast nor bottle they perish.