736 JOUENAL OF THE EOYAL HORTICULTURAL SOCIETY. 



forms a new centre of disease, from which the toadstools eventually grow, 

 and a fresh crop of rhizomorphs extend in search of more victims. 



There are two methods of preventing the extension of this and other 

 similar pests. 



Whenever the toadstools appear round the hase of a trunk, they should 

 be collected and burned, or eaten, being included among edible fungi. It 

 is of no use kicking the fungus over and trampling on it ; by this means 

 the spores are only dispersed, not destroyed. 



It is important to remember that the rhizomorphs of A. melleus tra- 

 versing the soil only increase in length by growth at the extreme tip, and 

 to do this the tip must be constantly surrounded by material available for 

 food. To prevent the extension of these rhizomorphs from a diseased 

 tree, dig a trench, six or eight inches deep and six inches wide, round the 

 trunk and some distance away from it, and fill it with ashes, lime, or 

 any substance devoid of humus. Through this barrier the rhizomorphs 

 cannot extend, owing to lack of food. 



The majority of those white mildews so destructive to the Hop, Rose, 

 Peas, &c., are characterised by having the whole of their mycelium super- 

 ficial, or running over the surface of the part they are parasitic upon, and 

 obtain food from the host by pushing suckers into its epidermal cells. 

 There is, however, one exception to this rule in the white powdery mildew 

 so common on the young shoots of Apple-trees in this and other countries. 

 Here we appear to have a perennial mycelium in the host-plant, which 

 grows along with the shoot each season, stunting its growth, and even- 

 tually killing the tree. In this instance it has been clearly demonstrated 

 on a very extensive scale, and extending over several seasons, that spray- 

 'ing does not diminish the disease ; whereas, owing to the fact that the 

 mycelium present in the branch does not extend backwards from the point 

 of infection, persistent removal of the diseased shoots soon exterminates 

 the disease, especially if combined with spraying in spring to prevent 

 fresh infection. 



A similar method of treatment should be practised in the case of 

 Peach leaf- curl, where the perennial mycelium does not extend back- 

 wards in the branch beyond the point indicated by the curled leaves. 



Of the numerous kinds of microscopic fungi attacking foliage and 

 fruit, our remarks, lacking time, must be restricted to one, the brown rot 

 of fruit — Monilia fructigena, familiar to everyone under the form of 

 numerous greyish warts, often growing in circles, on decaying Apples, 

 Pears, Plums, Cherries, &c. Although best known to the casual observer 

 as occurring on fruit, this fungus usually first attacks the leaves, young 

 shoots, and flowers. In too many instances where shrivelling blossom is 

 attributed to having been " touched by frost," the real cause is our friend 

 or enemy Monilia. 



On the leaves the fungus forms very thin, velvety, olive-brown patches, 

 consisting of chains of spores, which become free at maturity, and are 

 blown or washed by rain on to other leaves or fruit. On the fruit the 

 disease first forms scattered brown spots, which eventually develop into 

 the warts already described as forming circles — miniature " fairy rings " in 

 fact. These rings often grow into each other. Such diseased fruit does 

 not rot, but shrivels, and either hangs on the tree throughout the winter 



