228. 



PRACTICAL BOTANY 



are formed (Fig. 183). The wall of a spore-containing hypha 

 is the sac or ascus, and the spores which are formed therein 

 are the ascospores, or sac spores. These spores, when favorably 

 placed, again produce the mycelium of the parasite. This repre- 

 sents the chief method of spring and early summer infection 

 of fruits with the brown rot. 



221. Destructiveness of Sclerotinia. All kinds of stone fruits 

 seem to be susceptible to attacks of this disease. It is said 1 : 



" It would appear that among 

 peaches the sorts densely 

 covered with hairs or down, 

 such as Alexander, Hill's 

 Chili, and Triumph, are usu- 

 ally susceptible. Among the 

 more resistant sorts are to 

 be found the Carmen, Early 

 Crawford, Elberta, Chinese 

 Cling, and some others. 

 Among the plums the Jap- 

 anese varieties suffer gen- 

 erally in most sections of 

 the country. The American 

 group of plums is also sus- 



FIG. 184. A group of "morel" mush- 

 . rooms (Morchella) 



Note the depressions in the surface, in 



which the sacs and ascospores are formed. , 



Three fourths natural size ceptible, and apparently more 



susceptible at the South than 



farther north. The Wild Goose and Marietta plums are much 

 less affected in all regions. The native cherries are more resist- 

 ant than such as the Montmorency." The total amount of the 

 damage is enormous. In 1887 Maryland and Delaware were 

 reported to have had a peach-crop shortage, from this cause, of 

 800,000 baskets of fruit. In 1900 Georgia had an estimated 

 loss of 40 per cent of the peach crop, or a money loss of be- 

 tween $500,000 and S700,000. 2 The disease may be checked 



1 Duggar, Fungous Diseases of Plants. Ginn and Company, Boston, 1910. 



2 "The Brown Rot of Peaches, Plums, and Other Fruits," Bulletin 50, 

 Georgia Agr. Exp. Sta., 1900. 



