Recurrent appearance of bisporangiate strobili with proliferation on Picea abies

Observations of mature Norway spruce, Picea abies (L.) Karst., that developed numerous bisporangiate strobili with proliferation were documented over a period of nine years. Most abnormal strobili had male characteristics at the proximal ends, female characteristics above, and vegetative proliferation at the distal ends. The degree of male, female, and vegetative characteristics varied among the hundreds of bisporangiate strobili observed, and there were many transitional stages. They appeared on one tree during eight spring-flushing seasons, on another during two seasons, and on five trees in the season following two environmental stresses: an insect infestation and a dry period which occurred when primordia were differentiating on developing embryonic shoots within buds.