Heat oven to 250°F. Line two baking sheets with waxed paper; coat with nonstick cooking spray. In a large bowl, with electric mixer on low, beat egg whites, salt, and lemon juice until foamy. Increase speed to high; beat until soft peaks form.
Gradually beat in sugar; reduce speed to low and add vanilla. Beat several minutes longer, until mixture is glossy and stands in stiff peaks.
Transfer half the mixture at a time to a pastry bag fitted with a 1/2-inch tip or to a large resealable plastic bag with a small hole cut in one corner. Pipe small peaked rounds 1-1/2 inches apart on prepared sheets. For a striped effect, drizzle a few drops of red food coloring around inside of pastry bag before filling.
Place sheets on middle oven racks; bake 35 minutes. Switch sheet positions halfway through baking time. Turn heat off and let meringues stand in oven 30 minutes. Slide waxed paper, with meringues still attached, onto a flat surface. Cool meringues completely; gently lift off paper.
Place chocolate morsels in a small microwave-safe bowl. Microwave on medium 1 minute; stir until smooth. Dip bottoms of meringues in chocolate. Place on waxed paper to set chocolate, about 30 minutes. Store up to a week in an airtight container or freeze.