"Independent of Galls, which are caused by the punctures of insects, and the swellings which always accompany Canker, the excrescences which injure the gardener's crops are very few. That which appears above the point of union between the scion and stock, is caused by the former being the freer grower of the two, and is a warning which should be remembered, for it curtails the longevity of the tree, the supply of sap gradually becoming inefficient.

"The excrescences which occur upon the branches of some apples, as those of the codling and June-eating, cannot be looked upon as disease, for they arise from congeries of abortive buds, which readily protrude roots if buried in the soil, making those among the very few apples which can be propagated by cuttings. Of a similar nature are the huge excrescences so prevalent on aged oaks and elms. Bulbous excrescences are formed upon the roots of many plants if compelled to grow upon a soil drier than that which best suits them. This is the case especially with two grasses, Phleum pratense and Al-opecurus geniculatus, and is evidently a wise provision of nature to secure the propagation of the species, for those bulbs will vegetate long after the remainder of the plant has been destroyed by the excessive dryness of the soil.

"On the free performance of this function of plants their health is dependent in a very high degree: and I believe that half the epidemics to which they are subject arises from its derangement. That consequence of the clubbing of the roots of the brassica tribe, called fingers and toes, arises, I consider, entirely from it. In the drought of summer, when the moisture supplied to a club-rooted cabbage by its root does not nearly equal the exhalation of its foliage, to supply this deficiency the plant endeavours, by forming a kind of spurious bulbous root, to adapt itself to the contingency." - Princ. of Gardening.