46 
(b) The mummies which cling to the trees through: the winter or 
the cankers on the limbs harbor the pathogene as living mycelium or as 
thick-walled conidia. The warm spring rains cause the formation of 
multitudes of thin-walled conidia which it is believed may also function 
as primary inoculum. Mummies have been brought into the laboratory 
and placed for several days in a moist-chamber. 
Examine one of the mummies and NOTE :— 
20. The grayish brown powdery spore-tufts. Make an en- 
larged DRAWING of a part of a fruit showing these cushions as they appear 
under the hand-lens. . 
With the point of a scalpel remove a bit of the spore-mass to a slide, 
cover and examine. OBSERVE :—- ; 
21. The rather large hyaline globose or oval bodies scattered 
through the mount,—the conidia. Variations in form, size, and thickness 
of the walls. 
22. The granular, sometimes alveolate character of the proto- 
plasm of the spore. (See also under the oil-immersion demonstration 
microscope. ) 
Make an enlarged prawinc of a conidium to show the structure. 
Slides showing germinating conidia have been prepared. Examine and 
OBSERVE — 
23. The long septate germtubes. Simple or branched? 
How many from each conidium? DRAW. 
The ascospores or conidia are carried to the opening blossoms, where 
if the weather be rainy they quickly germinate and the germtubes penetrate 
the calyx or exposed corolla. The blossom-blight form of the disease is 
thus initiated. 
Mount one of the diseased petals provided. Stain with eosin and 
STUDY :— 
24. The mycelium in the tissue; its form, size, septation and 
branching. Does it go through or between the cells? DRAW. 
The mycelium ramifies throughout the blossom and on protruding 
conidiophores forms masses of grayish brown conidia,—the inoculum for 
secondary cycles. From the blighted blossom the mycelium follows down 
through the fruit-spur to the twig or branch killing the bark and causing 
twig-blight or young cankers. In the cankers onthe limbs the fungus 
may remain alive throughout the winter and provide, as indicated above, 
conidial inoculum for the primary cycles the next year. 
The primary cycle does not include a saprogenic phase unless developed 
on fruits, which is probably rare. 
The Secondary Cycles are in all probability initiated from conidia 
developed on the blighted blossoms .or from other secondary infections 
on fruits and twigs. The blighted twigs, blossoms and green fruit con- 
tinue to harbor and multiply the parasite during the early part of the 
season until the maturing fruit offers opportunity for its very general 
spread and destructive work. 
Pathogenesis. Diseased specimens of ripe fruits showing the 
pathogene are provided. With forceps, remove a bit of tissue from a badly 
rotted fruit. Tease apart ina drop of water on a slide, cover and study 
under the microscope. OBSERVE :— 
25. The form, structure, contents, septation branching, size 
and color of the mycelium. Note variation in diameter of the mycelial 
threads. (Staining with eosin or methylene blue will bring out the mycel- 
