402 SECTIONAL TRANSACTIONS.— K. 



uptake is affected. Its absence during the young stages is critical and results in 

 serious or total reduction of ear formation as well as reduction of yield. The length 

 of the critical periods during which the element is essential varies according to the 

 time of sowing, seasonal conditions and the variety. Experiments in hand (June, 

 1930) suggest a somewhat similar course of events for nitrogen, though possiblj^ this 

 element is of more general importance throughout a longer period of development. 



The significance of most of the minor constituents is hardly known as yet. Many 

 elements are very toxic if they are present in relatively small amounts, but some 

 appear to be of definite value in minute traces. Boron, for instance, is essential for 

 the normal growth of such plants as broad beans, rurmer beans, and clovers, being 

 intimatelj' associated with the development of meristematic tissue and the production 

 of flowers. Further evidence is now available which indicates that the need for boron 

 may be varietal, as well as specific. Perfect development of plant and grain has 

 constantly been obtained with Spratt-Archer and Goldthorpe barley in the absence 

 of boron, but Plumage Archer failed this year at the time of flowering, irrespective of 

 the date of sowing. Ear emergence was imperfect and very few grains developed, 

 indicating faulty pollination ; this was coupled with the sudden production of large 

 numbers of small tillers at the time the grain should have been filling out. 



In the presence of boron better development of ears and grain was obtained. 



The variation in varietal response to minor nutrients may account for the apparent 

 discrepancies in the results of different workers with such elements as boron, manganese, 

 iodine, etc. The possibility also exists that other elements, hitherto unrecognised as 

 plant nutrients, may prove to be essential in minute quantities for the development 

 of various plants. 



Minor plant constituents are also important from another aspect as their absence 

 may predispose the plants to certain diseases or may be the specific cause of diseases, 

 e.g. the Grey Speck disease of oats, wliich Samuel and Piper have shown to be due 

 to deficient manganese absorption on certain soils. There are indications that environ- 

 mental conditions may aft'ect the value of certain minor elements as nutrients, but 

 little definite information is yet available on this point. 



Mr. A. Malins Smith. — The Composition of Upland Bog Waters and its 

 Relation to Algal Vegetation. 



Afternoon. 

 Excursion to Brockley Combe. 



Saturday, September 6. 



Excursion to Forest of Dean. 



Sunday, September 7. 



Excursion to Somerset Peat Moors by way of Burrington Combe and 

 Cheddar. 



Monday, September 8. 



Prof. W. GooDSPEED. — Cytogenetic Evidence as to Species, Origins and 

 Relationships in the Genus Nicotiaua. 



Mr. [M. Thomas. — Fermentations in the Cells of Higher Plants in the 

 Presence of Oxygen. 



Although alcoholic fermentation (= zymasis), i.e. the accumulation of ethyl 

 alcohol and, sometimes, acetaldehyde, occurs only rarely in the cells of higher plants 

 in air, it has been observed in the absence of oxygen, in low concentrations of oxygen, 

 and in certain relations of carbon dioxide and oxygen, hydrogen cyanide and oxygen, 

 and sulphuretted hydrogen and oxygen. 



