96 STATE HORTICULTURAL SOCIETY. 



the fruit in entire orchards, but seems to pick out particular trees and con- 

 tine its ravages to them, recurring every year. 



"The mycelium spreads through the tissues and finally its hypluc are 

 pushed out through the epidermal cells. Early in the season these produce 

 conidia, but later on the ascospores are })roduced in enlarged hyphae. The 

 infected plums should be gathered and burned, and any branches that show 

 signs of the fungus in their tissues should be cut ofP. In severe cases it 

 "would be well to head back all the previous year's growth and work in 

 around the trees a liberal amount of wood ashes. It would also be well to 

 spray the trees with sulphate of copper. 



POWDERY MILDEW OF THE PLV i^l.-Podosphoera n.nj<antha. 



" This fungus has quite a range of host plants, among them the haAV- 

 thorn, four species of cherry, three of plum, the peach, apple, quince, sev- 

 eral species of spiraea, shad-bush, blueberry, and persimmon. 



"The leaves of cherry trees are particularly affected. The fungus 

 appears in midsummer, on the new shoots and leaves. The latter are 

 attacked on either or both sides, and are sometimes entirely covered with a 

 mealy-looking fungous growth. 



"The mycelium is made up of slender, white, branching threads, wliich 

 do not enter the tissues themselves, but send down their haustoria into the 

 epidermal cells. The summer spores are borne on rather stout hyphse, and 

 are produced by being cut off from the stalks by means of transverse par- 

 titions. The conidia drop off, and, falling on a moist spot, they germinate, 

 and if this place be the leaves of one its host plants, a new fungus is formed. 



^'The j)cril}i<'cin, in which the winter spores are produced, are formed 

 where two of the filaments intersect. At first they are colorless, but they 

 gradually turn brown. The walls of the periihecia are made up of a large 

 nmnber of cells. These are somewhat rounded on the outside and give the 

 }>('rifli<'ci(( an appearance something like a rasberry. From some of these 

 cells, appendages are given off, which consist of several cells and have 

 curiously branched tips. The appendages vary in number from three or 

 four to as many as twenty. In this perithecium is a single ascus which 

 contains eight ascospores. 



"This mildew, like all other powdery mildews, thrives best in hot, dry 

 seasons. The spores require moisture for their germination, but they 

 develo}) to best advantage in seasons of drouth. These mildews are among 

 the easiest of all fungi to destroy, as their gr<jwth is entirely outside the 

 plant, and any form of copper or sulphur can reach and destroy them. 

 The sulphide of potassium, applied whenever the finig-us appears, is one 

 of the simi)lest remedies. 



SHOT-HOLE FUNGUS— Sepior/a pruni. 



" Our plums and cherries, and sometimes our peaches and apricots, suffer 

 toward the close of summer from a premature falling of their leaves. This 

 is usualh' most noticable either in a very dry or in a very wet season. 



" If the fallen leaves are carefiilly examined they will generally be found 

 to contain a greater or lesser number of small round holes, like shot-holes 

 in appearance. These have been caused by a fungus which in some cases, 

 produces (piite serious effects on the trees. It has inflicted a two-fold 

 injury. It has robbed the tree of its food and has weakened it by the 

 premature loss of its leaves. The spots at first are brownish red and gen- 



