I io6 



THE BOOK OF GARDENING. 



to the soil. This \Yill minimise considerably the trouble from 

 such a source ; while, if it is possible to apply a dressing of lime 

 in winter beneath trees so affected, this would further help the 

 grower to battle with the disease. 



Other means of reproducing such diseases of parasitic fungi 

 are by the mycelium, or vegetative part of the plant. For this 

 reason where trees are attacked by fungi like Arinillaria mellea^ 

 Trametes pijii, Szc, the practice of isolating such by means of 

 trenches is adopted. Hartig, in his excellent work upon "The 

 Diseases of Trees," says that if this is carefully carried out it 

 is a certain preventive against the spread of the disease. 



Another most prolific source of reproduction is found in 

 Sclerotia which are produced by certain fungi affecting Potatoes, 



^Marrows, Beans, and many bulbous plants. 

 As the name suggests, they consist of /lard 

 structures which are of variable size, colour, 

 and form. Frequently, however, they are 

 roundish or oval (Fig. 719), and black ; they 

 are also numerous. It is within the last 

 few years that Sclerotia in connection 

 with several well-known fungoid diseases 

 have been discovered — the Lily Disease 

 for instance. In this Prof. ^Marshall Ward 

 compares them to mice - droppings, and 

 suggests how readily they might be 

 mistaken for '* foreign bodies." Then 

 there is an extremely troublesome fungus 

 popularly called the Sclerotium disease 

 i^Sclei'otmus Sclerofio?nn?i), which affects a 

 host of plants, the Sclerotia being of large size. Burning those 

 affected is all that can be done. 



Sclerotia are sometimes found only in dead plants ; at others 

 only in living ones. In no case, however, do they resume activity 

 until the host-plant itself is well advanced. Usually they rest in 

 the soil through the winter, the hard, outer coat serving to pro- 

 tect the soft inner contents of felted mvcelium from frost and 

 cold. 



Mention has already been made of the desirability 

 ing and burning all rubbish, such as leaves and 

 fallen fruits should be included in the same category, 

 from plants infested with fungi should never be taken, and seeds 

 from a similar source are also to be avoided. Some varieties of 

 vegetables and fruits have proved themselves if not exactly 

 disease-proof, at least partially resistant, and all the principal 

 nurserymen may be relied upon to supply them. Potatoes have 

 been vastly improved in constitutional vigour. Unfortunately, 

 some of our finest hardy fruits have proved least capable 

 of resisting disease than others. Cox's Orange Pippin cankers badly 



Fig. 719.— Sclerotium 

 OF Peziza postuma 



(natural size), with two Cups 

 on slender stalks. 



of collect- 

 prunings : 

 Cuttings 



