Taphrina padi Taphrina padi Taphrina padi is a fungal plant pathogen that induces the form of pocket plum gall that occurs on Bird Cherry ("Prunus padus"). The gall is a chemically induced distortion of the fruits, which are swollen, hollow, curved and greatly elongated, without a seed or stone, but retaining the style. The twigs on infected plants may also be deformed with small strap-shaped leaves. "Taphrina padi", a 'tongue fungus', produces a distinctive, elongated, tongue-like growth on Bird Cherry, similar to other closely related species such as "Taphrina alni" on Alder ("Alnus glutinosa") and "Taphrina pruni" on Blackthorn ("Prunus spinosa"). The
Prunus avium parent species of "Prunus cerasus" (sour cherry), by way of ancient crosses between it and "Prunus fruticosa" (dwarf cherry) in the areas where the two species overlap. All three species can breed with one another. "Prunus cerasus" is now a species in its own right, having developed beyond a hybrid and stabilised. Pliny distinguishes between "Prunus", the plum fruit, and "Cerasus", the cherry fruit. Already in Pliny quite a number of cultivars are cited, some possibly species or varieties, Aproniana, Lutatia, Caeciliana, and so on. Pliny grades them by flavour, including dulcis ("sweet") and acer ("sharp"). and goes so far