Contribution to the Process of Leaf Fall

The spontaneous detachment of leaves from their axis is a phenomenon which can be observed in ligneous and herbaceous plants of many kinds as a reaction to very different extrinsic and intrinsic factors and under varying circumstances. Also observations that leaves inhabited by Cynipidae become detached from the trees in very large numbers ahead of time and without any discoloration. The gallnuts of Oligotrophus bursarius produced on the leaves of Glechoma and spontaneously detached upon 'ripening' indicate that even parts of a leaf blade may become detached, under abnormal conditions, in the same manner, i.e. after formation of the same abscission layer which is normally formed between leaf and axis. Trans. of Deutsche Botanische Gesellschaft. Berichte (Germany) v34 p184-193 1916.