390 SECTIONAL TRANSACTIONS.— K, K*. 



3. Chance's Ultra-violet Glass : transmitting a little of the violet and ultra-violet 

 rays to at least \±\j.300, mainly [i.[i.3300-3900. 

 Various methods have been employed in order to determine the equivalent 

 exposures under these screens. The difficulty of obtaining light of comparable 

 intensity in each case is discussed. 



Mr. F. T. Brooks Lecture on Disease Resistance in Plants. 



Wednesday, September 7. 



Prof. F. E. Fritsch. — The Genus Sphcrroplea. 



Sphceroplea has usually been regarded as a septate member of Siphonales of 

 uncertain affinities. Apart from the multinucleate character of its ' cells,' there is, 

 however, nothing in favour of such a relationship. A survey of the features presented 

 by the different species (well represented in South Africa) indicates an affinity with 

 Ulotrichales, on the grounds both of vegetative and reproductive characteristics. 



Dr. Harold Wager, F.R.S. — The White Strip on the Leaf of Crocus. 



Mr. C. V. B. Marquand. — Arctic Alpine Bryophyte Associations in Britain, 

 as compared with those of Western and Central European Mountains. 



Mr. H. Duerden. — The Sporangia of Selaginella. 



In heterophyllous species of Selaginella the megasporangia tend to occur in line 

 with the large ventral leaves. 



In many cases the number of megaspores in the sporangium is increased. In 

 Selaginella Walsoni one case of eight megaspores : Selaginella Lobbii eight, twelve, 

 fourteen, sixteen, eighteen and twenty. In Selaginella Willdenowii sixteen, thirty-six 

 and forty-two megaspores. 



Mr. T. M. Harris.— The Fossil Plants of N.E. Greenland. 



SUB-SECTION K\— FORESTRY. 



Thursday, September 1 . 



Prof. Fraser Story. — World's Timber Supply and Consumption. 



The timber supply problem concerns soft woods principally because, to the extent 

 of over 80 per cent., the world's demands are for timber of this description. The 

 conifers which produce soft woods are found extensively only in temperate regions 

 and are practically confined to North America, Northern Europe and Siberia. 



In the United States one district after another has been cut over until nearly all 

 the lumbering activity is centred in the few Western States, the resources of which 

 at the present rate of cutting cannot be expected to hold out for more than twenty 

 to thirty years. Forest exploitation in Canada has followed a remarkably similar 

 course. The once heavily timbered regions of Eastern Canada have been cleared 

 of practically all large-sized timber and the soft woods of smaller dimensions are now 

 seriously threatened owing to the great demands made on them by the paper-pulp 

 industry. According to official statistics, three-quarters of Canada's merchantable 

 timber has already been destroyed or utilised. 



Apart from North America, approximately 75 per cent, of the world's soft-wood 

 area is located in Northern Europe and Siberia. In Europe the consumption of 

 soft woods exceeds growth by about 3,000 million cubic feet. Most of the existing 

 coniferous forests are to be found in Northern Russia, but this area cannot be relied 

 upon owing to its inaccessibility and the sparsity of the population. For similar 

 reasons Siberia, although containing vast forests, cannot be economically exploited. 



