BIOLUMINESCENCE OF DECAYING LEAVES 421 



fraction of the fallen leaves are in a condition in which they give 

 out hght, and that the forest floor everywhere is receiving radiation 

 from the hght of decaying leaves." Molisch expresses astonish- 

 ment that so wide-spread a phenomenon as the bioluminescence of 

 decaying leaves should be practically unknown to foresters, wood- 

 men, botanists, etc., and he presumes that this is simply due to the 

 fact that most people avoid woods at night. 



It seemed of interest to find out whether or not luminous 

 leaves occur in England in the same manner as in Germany, In 

 the years 1922 and 1923, therefore, I made the following series of 

 observations. 



About June 1, 1922, at King's Heath, a suburb of Birmingham, 

 I went out into my father's garden at night and, covering my head 

 and a heap of old Sycamore leaves with a coat, examined the leaves 

 for luminescence. One of the petioles gave out a bright light, but 

 no other signs of luminosity could be observed. In the same garden 

 I also examined a heap of Beech leaves which had been raked to- 

 gether the previous autumn. Within it I found a few luminous 

 rhizomorphs of Armillaria mellea and some tiny insects which gave 

 out hght when disturbed and which I took to be species of Collem- 

 bola, but no luminous leaves. However, the conditions under 

 which the heap of leaves had been made were artificial. I there- 

 fore determined to turn my attention to the leaf- mould in a wood. 



On June 10, I visited a wood on the border of Sutton Park, 

 Warwickshire. In a hollow underneath some large Beech trees, 

 which were about 150 years old, there was a thick layer of leaf- 

 mould that had evidently been accumulating for some j^ears. 

 I removed the uppermost, relatively dry, curled-up leaves and filled 

 a small attache case with the moister, more flattened leaves thus 

 exposed. These had fallen in the previous year and were brown, 

 elastic, and still almost intact ; but they showed signs of decay in 

 that to a certain extent they were discoloured with somewhat pale or 

 yellowish blotches. To the Beech leaves I added a few Oak leaves 

 obtained from the mould beneath an Oak tree (c/. Fig. 179). The 

 same evening I emptied out the leaves upon a large tray in a dark- 

 room and examined them for luminescence. As soon as my eyes 

 had become adapted to the darkness, I perceived that a number 



