STIPPEN 
This disease goes under a variety of names; Baldwin-spot, bitter pit, 
and fruit-pit being the most commonly used. It is one of the non-parasitic 
diseases. It occurs the world over, wherever apples are grown. 
SYMPTOMS 
So far as is known, lesions are evident only in the fruit. Examine 
the specimens provided, studying carefully the external characters of the 
lesions. OBSERVE :— 
Pe 1. The slightly depressed areas or ‘‘pocks’’; their size, color and 
ape. 
2. Their distribution over the fruit, usually most numerous in 
what region? 
3. The differences between these lesions and those of the New 
England fruit-spot, specimens of which are provided. 
Make a sketcu of an affected apple to show the general character and 
distribution of the lesions. 
Make an enlarged detailed prawine of a lesion of the stippen and 
ae it one of the New England fruit-spot for comparison. Label 
y. 
Divide the apple (with the scalpel) lengthwise through the core. oB- 
SERVE :-— 
4. The internal appearance of the lesion; color, size and shape. 
5. The distribution of the lesions; relation to the surface-pits 
and to the vascular bundles. 
SKETCH the cut surface to show the form, size and distribution of the 
lesions as seen in this aspect. 
Placing the halves together, cut the fruit across the core. sTUDY:— 
6. The character and distribution of the internal lesions as 
exhibited in this aspect, especially their relation to the vascular strands. 
SKETCH to show the lesions as seen in the cross-section of the fruit. 
Study the individual internal lesions more critically as To:— 
7. Usual form, color, texture and taste. Compare with the 
adjacent healthy tissues. Are there any indications of a bitter taste? 
ETIOLOGY 
Many theories have been advanced with respect to the cause of stippen. 
Pathologists appear to be generally agreed that it is due to extreme varia- 
tions in the water-supply to the tree during the growing-season. (For a 
full discussion of etiology see the text or McAlpine, Bitter Pit Investiga- 
tions. 1:110; 2:93-95; 4:73-75.) 
Pathological Histology. The effect on the host-tissue is necrotic. 
Select one of the lesions next to the skin of the fruit which shows no cavity 
as yet. Make numerous thin sections with a sharp razor through the 
lesion at right angles to the surface of the fruit. Float these at once in 
clean water in a watch-glass. Mount one of the thin but entire sections. 
Cover and stTuDY:— 
8. The diseased cells; their collapsed walls, contents, and color 
as compared with the adjacent healthy cells. Treat the section with 
jodine-solution and examine for starch. Where found and why present? 
107 
