It's difficult to know for sure from this picture, but they look like leaf galls or externally laid insect eggs to me. Leaf galls are produced when certain insect species lay eggs in a leaf, and when they hatch, the leaf responds to the irritation by producing these galls, which become protective homes for the hatchlings until the are mature enough to leave this temporary home. I personally do not harvest plants with galls or other signs of animal life, as I do not wish to unnecessarily take a life, but it won't affect the quality of your product, if that is your concern. It is near impossible to harvest insect free plants, as many of them are so tiny that we cannot see them. Green Blessings