Observations on the ''Slime-fluxes" of trees. 179 



by budding, and average 5-4 /u in diameter from a three days' 

 beer- wort gelatine culture. Spores formed readily on ordiaary 

 media, four in number, globular, and about i-S/Lt in diameter. 

 No myceliimi or conjugation ob5er\'ed. 



The yeast belongs to the genus Saccharomyccs Meyen. 



A similar flux was found on certain Huntingdon elms near 

 Jesus College, Cambridge, which died oflt one by one probably 

 owing to an escape of gas from a main in the Wcinity. The flux 

 appeared in July as large gelatinous masses exuding from bore- 

 holes of the bark-beetle, Scolytus, with which the trees were 

 badly infested. Large numbers of wasps were attracted to the 

 exudations, which were confined to the bark and persisted only 

 for a few weeks. Neighbouring healthy trees were unaffected. 

 The organisms present included bacteria -with gelatinous sheaths 

 and a round sporing veast identical with that described from 

 the flux of willows. 



GENERAL DISCUSSION. 



The bro\^Ti flux is, when gathered near its point of exit from 

 the tree, of a watery- nature, but after exposure to the air for 

 some time it dries up to a yellowish bro^^"n or brown powder. 

 It is not hygroscopic. The red flux of Huntingdon ekns was 

 found to be shghtly alkaline, ha\-ing a pYi of about 9, while 

 advanced bro\Mi fluxes from Ulmus campestris were more 

 alkaline, with a pH of from 9 to 9-5. The alkalinity is probably 

 due to the large amount of calcium carbonate derived from the 

 wood (the ash of elm wood is stated to contain 47-8 per cent, 

 of lime). This also accounts for the hard stony nature of old 

 flux marks. 



The writer has come to the conclusion that the red and 

 brown fluxes are of phvsiological origin, arising primarily, in 

 the case of branch woimds, as the exudation of a clear fluid 

 from the centre of the heart-wood. Such water-soaked areas 

 have been seen by the writer in the centre of freshly-cut branches 

 of Huntingdon and ^^'ych elms during the summer months. 

 They do not occur on small branches in which no heart- wood is 

 e\ident, but are ver\- commonly to be seen on exposures of 

 large branches. Similar water-soaked areas have been seen in 

 the centre of cut branches of apple and poplar. 



There is httle doubt that these phenomena are the same as 

 those investigated by Professor \V. G. Craib in the case of 

 Acer (2o\ and later in the case of true heart-wood trees [Ulmus 

 montana and Querciis cerris) (21). According to Prof. Craib, storage 

 of water takes place in the autumn in the centre of the trunk, 

 commencing at the base. ''By the time the centre has received 

 its quota far up the trunk another movement has begun causing 



