SECTIONAL TRANSACTIONS.— K*, L. 511 



is suggested that certain copses in the area, consisting almost entirely of 

 Ulmus and lacking the characteristic woodland undergrowth of the neigh- 

 bourhood, are a further stage in the succession. 



Discussion (11.30). 



Afternoon. 



Prof. W. Neilson Jones and Mr. A. G. Morton. — Some features of soil 

 and growth on the Wareham heaths (2.30). 



Mr. C. H. Thompson. — The present position of forestry at Cambridge 

 University (3.15). 



Mr. G. Metcalfe. — The morbid histology of watermarked willows (3.40). 



From stained wood four bacterial species can be isolated — Bacterium 

 salicis, a white organism resembling B. cerogenes, a yellow organism and a 

 member of the fluorescens group. These form a mixed population in the 

 vessels. In recently diseased wood (brown stain) B. salicis predominates, 

 in later stages (black stain) the secondary organisms predominate. Bacteria 

 form occluding masses in the vessels ; tyloses appear and form a pseudo- 

 parenchymatous tissue. Small diagonal cracks, joining infected elements, 

 are formed by the solution of the pectic middle lamellae by the fluorescent 

 organism. Tannins are abundant in the degenerating ray cells ; the brown 

 stain is due to the oxidation of their breakdown products. The bacterial 

 oxidase systems may bring this about as the brown stain is correlated with 

 the presence of occluded vessels. The black stain sometimes present is due 

 to the formation of melanin in the ray cells. Bacteria colonise ray cells 

 after degeneration of protoplasm ; the bacteria spread radially in this way. 

 Longitudinal spread is along vessel lumina. The bacteria become actively 

 motile following spring hydrolysis of starch and spread rapidly about the 

 tree. The bacteria are non-motile during the summer and autumn. There 

 is a slow radial and longitudinal spread during winter, resulting in the 

 formation of thin layers of bacteria around the walls of vessels in the current 

 year's wood. 



Tuesday, August 23. 



Excursion to Weasenham Wood. 



SECTION L.— EDUCATIONAL SCIENCE. 



Thursday, August 18. 



Sir Richard Gregory, Bart., F.R.S., and Mr. H. G. Wells. — Report of 

 Committee on the content of school curricula (lo.o). 



Discussion on Tendencies in the design of schools (10.30). 



Mr. 8. E. Urwin. 



The School. — ^A place of learning and training of culture and appreciation. 

 The Building. — Temporary or permanent — Construction — should be of 



