Address by Dr. Hahn. 51 



the unexpected which happens, that, for example, a millionaire wer« 

 to give a portion of his treasure to research work, a considerable part 

 oi this should be devoted to lift the veil which still wraps in darkness 

 this field of research. I expect from the investigations in this field 

 results which will be as interesting as they will be important. 



Vegetable Physiology also presents in South Africa man) inter- 

 esting problems to the student of Chemistry, of which I may be 

 perrnitted briefly to mention a few. 



It is known that the composition of the mineral constituents of 

 the leaves of plants vary considerably during the annual period of 

 vegetation, although the different plants and trees exhibit a certain 

 predilection for the one or the other of these mineral constituents. 

 Whilst most of the forest trees of Europe contain in the leaves in 

 spring principally Potash and Phosphoric Oxide, these constituents 

 disappear almost completely in autumn, and the ashes of leaves 

 consist then almost entirely of Silica and Carbonate of Lime. From 

 a scientific point of view, it is of interest to know how these changes 

 proceed under the climatic conditions of the Cape. One investiga- 

 tion of leaves or other parts of plants during the annual period of 

 vegetation is not sufficient, and of little value. To obtain a clear 

 insight into the circulation of the mineral constituents within the 

 plant, and intcj the requirements of plants, it is indispensable to have a 

 series of investigations, methodically planned and systematically car- 

 ried out, which should in the first place be directed to the crops we 

 ■cultivate, to the fruit trees, and to the forest trees. These investiga- 

 tions require much time and perseverance, and should be carried 

 out in the laboratories of agricultural stations or of a forest academy. 



Another problem of scientific interest and economic importance 

 presents itself in the comparative nourishing value of the crops we 

 grow. This depends upon the quantity of carbo-hydrates and 

 albuminous compounds contained in these crops. It is known that 

 the production of the albuminous compounds in sunny climates is 

 much larger than in cold climates, with an ever-cloudy sky. It is a 

 matter of importance to investigate this subject in connection with the 

 leguminous plants, such as peas, beans, lucerne and clover. This ques- 

 tion is also of importance for the cultivation of cereals, more particu- 

 larly of barley used for brewing beer. There is no doubt that the 

 barley grown in South Africa possesses a higher nourishing value than 

 the English barley, because it contains a larger proportion of gluten, 

 that is, albuminous substance, than the English barley. 

 But this is the ^ery reason why the Cape barley is less suit- 

 able for brewing beer than the English barley, because the presence 

 of too much albuminous matter in the beer is not desirable for brew- 

 ing. Similar obser\ations have been made in grapes grown on the 

 hillside or on vlei-soil and in vineyards which are occasionally irri- 

 gated. The grapes grown on a hillside contain less albuminous 

 matter, they yield a better quality of wine, and the making and matur- 

 ing of this wine presents no difficulty, whereas the grapes grown on 

 vlei-ground or irrigated vineyards, contain more albuminous sub- 

 stance, and the making and maturing does not proceed so smoothly. 



