Sprinkle the gelatin on the cold water and dissolve in the hot pineapple juice.
Cool and add the lemon juice and vinegar.
Stir in a Utile green food coloring.
Chill until syrupy.
Fold in the pineapple and cucumber and pour into a ring mold which has been rinsed in cold water.
Chill until set.
Unmold on a chilled platter and fill the center with torn-up mixed salad greens which have been well tossed with French dressing.
Pass mayonnaise too.