BIOLUMINESCENCE OF DECAYING LEAVES 427 



Tulasne and Molisch, also occur in England, Canada, and the 

 United States. As time goes on, doubtless, many other countries 

 will be added to this list, and it is even possible that luminous 

 leaves may be found in broad-leaf forests throughout the whole 

 world. 



Persistence of Luminescence in Leaves. — One midnight in July, 

 1923, whilst in England, I collected a large number of luminous 

 leaves (Oak, Beech, Spanish Chestnut, Rhododendron) from a wood 



Fig. 180. — A shadow-photograph of black-paper letters made with 

 the liglit emitted by luminous Beech, Oak, and Spanish Chest- 

 nut leaves. Leaves collected at Four Oaks, Warwicksliire, 

 England. Exposure of negative, 50 hours. Original size. 



at Four Oaks, Warwickshire (Fig. 179, p. 422). The wood was so 

 dense, the night so dark, and the leaves glowed so brightly, that I 

 was able to select the leaves from the leaf-mould by the amount of 

 light which they emitted. The leaves were allowed to dry and were 

 then transported to Winnipeg. After remaining dry and non- 

 luminescent for ten months, some of the leaves were set in a large 

 covered crystalHsing dish and sprayed with water. Within a few 

 hours a number of the leaves became luminescent once more. The 

 leaves were kept moist and it was observed that, at room tempera- 

 ture, they continued to give out their light for 7-8 weeks. The 

 bioluminescence of decaying leaves, under favourable laboratory 

 conditions, is therefore a very persistent phenomenon. In nature, 



