164 Transactions British Mycological Society. 



including the violet, blue and green rays. The exciting rays 

 capable of bringing about fluorescence extend from the ultra- 

 violet to the blue-green part of the spectrum up to about the 

 line F and the spectrum of the fluorescent radiation includes 

 the blue-green, green and yellow-green part of the spectrum. 

 There is here therefore some overlapping of the absorption band 

 and the emission spectrum. 



According to the views at present held by physicists the 

 light absorbed, both in phosphorescent and in fluorescent 

 substances, brings about a partial or complete separation of 

 electrons from the atoms of the substances acted upon. Both 

 fluorescence and phosphorescence are therefore to be regarded 

 as photo-electric phenomena*. 



In the Fungi phosphorescence appears to be due to the activi- 

 ties of living cells, but fluorescence is only visible in solutions 

 of the colouring matter extracted from the plant by solvents. 



A REVISION OF THE BRITISH CLAVARIAE. 



By A. D. Cotton, F.L.S., and E. M. Wakefield, F.L.S. 



INTRODUCTION. 



The work on which the present revision is based was begun 

 in 1905. It was originally intended to include in the study all 

 the described species of Clavaria, numbering now about 400, 

 and to publish a systematic monograph of the whole genus. As 

 the work progressed however it became apparent that, before 

 any attempt could be made to monograph the genus, it was 

 essential to clear up the confusion which existed with regard 

 to the old European species. 



Microscopic structure had shown new ways of distinguishing 

 species and also that several undescribed species occurred 

 even in Britain. It was obvious, therefore, that it was only by 

 prolonged and careful field work, coupled with an investigation 

 of the micro-characters, that a true understanding of the genus 

 could be obtained and the old descriptions and original speci- 

 mens be correctly interpreted. 



As a result of this preliminary work it was decided to limit 

 the revision in the first place to the British species, but to include 

 during the investigation as many continental and extra- 

 European species as came to hand, with a view to publishing 



* Allen, Photo-electricity. 



