45 
11. The old blossom imbedded in a drop of gum at the point 
where the twig was girdled; or— 
12. The old mummied fruit or fruit-pedicle where the twig was 
girdled. 
DRAW to show the twig-blight form of the brown rot. 
On the limbs. Brown rot cankers are very common on large and small 
limbs of peach trees in some peach-growing sections. They originate 
usually from the blighted twigs, blossom or fruit-spurs. Examine the 
cankered limbs provided and OBSERVE :— 
13. The rough open cankers with evidences of repeated callus- 
formation. What does this indicate as to the age of the canker? 
14. Evidences of the diseased twig or spur about which the 
canker developed. 
15. Cankers breaking out above or below the original lesion,— 
evidences of metastasis. 
DRAW to show the character of brown rot cankers. 
ETIOLOGY 
The pathogene causing the brown rot of stone-fruits is Sclerotinia 
cinerea (Bonorden) Woronin. A closely related species, Sclerotinia 
fructigena (Persoon) Schréeter, is the common cause of brown rot of 
apples, pears and similar fruits in Europe. These fungi belong to 
that group of the ascomycetous fungi known as the Pezizales which 
are characterized by having an open cup-shaped apothecium in which 
the asci are borne. In the conidial stage the pathogene has been com- 
monly known as Monilia cinerea Bonorden. 
Life-history. This fungus has a more complicated life-history than 
most pathogenes causing diseases of the more common crops. This is due 
to the fact that its conidia may live over winter and initiate primary 
cycles. 
The Primary Cycle may be initiated from more than one source 
and by two sorts of inocula, as brought out in (a) and (b) below. 
Pathogenesis. (a) The mummies which fall to the ground give 
tise in the spring to apothecia which discharge myriads of ascospores 
about blossoming-time. The apothecia are very short lived, appearing 
over a period of not more than two or three weeks. Specimens have been- 
provided. OBSERVE :— 
16. The goblet-shaped fruit-body,—the apothecium with a long 
slender stipe. Upon what does the length of the stipe depend? 
17. The size and color of the apothecium. The upper surface 
(bearing asci) is when fully expanded, usually flat or even convex with 
recurving margins. They retain almost their natural color in alcohol. 
18. The attachment of the stipe to the mummy. To which 
side, upper or lower, is it attached? Why? 
Make a diagrammatic DRAWING showing the anatomy of the apothe- 
cium, its relation to the mummy and to the surface of the soil. 
Crush a bit of one of the apothecia especially provided for this purpose 
and OBSERVE :— 
19. The minute ovate ascospores,—the inoculum. Some of them 
are still in the asci in which they are formed. pRaw. They germinate by 
a simple germtube. 
