128 



depends on the fact that any particular plant requires the 

 presence in the soil of a certain minimum of each of the 

 necessary plant-food constituents in an assimilable form, and 

 if the minimum of any of these constituents is not present the 

 plant will not thrive. 



The method in use at Hasselt is as follows : 

 For each kind of soil, a number of pots are rilled with the 

 same quantity of soil, a layer of gravel being put at the bottom 

 to assist the aeration of the soil. 



Then manure is applied, taking great care to mix it well 

 with the soil. In each series: 



The ist pot receives a complete manure. 



,, 2nd ,, ,, ,, manure without nitrogen. 



,, 3rd ,, ,, ,, ,, ,, phosphoric acid. 



,, 4th ,, ,, ,, ,, ,, potash. 



5th ,, lime. 



,, 6th ,, ,, ,, ,, ,, magnesia. 



,, 7th ,, ,, no manure. 



The same number of seeds are sown, and after they have 

 germinated the same number of plants is left in each pot; these 

 are then placed in the best possible conditions of warmth, light, 

 and moisture. The experiment is repeated for each soil. 



Photographs taken during the course of the experiments 

 indicate that nitrogen is missing not only in the sandy soil 

 of Zambi, but also in the clayey soil of Ganda-Sundi. The 

 absence of phosphoric acid in the manure does not seem to affect 

 visibly the development of plants in the Zambi soils. The 

 clayey soil of Ganda-Sundi shows on the contrary a consider- 

 able deficiency of this constituent. There seems to be a great 

 scarcity of potash in the latter soil, whereas in the Zambi sand, 

 vegetation does not seem to be affected by the want of this 

 constituent in the manure formula. Lime and magnesia have 

 been, up to the present, without apparent influence on the 

 plants in these experiments. 



LA VALORIZZAZIONE DEL GIUBALAND PER LA COSTITU- 

 ZIONE DI UNA SOCIETA ITALO-INGLESE PER LO 

 SBARRAMENTO DEL GIUBA. 



Per Dott. NALLO MAZZOCCHI ALEMANNI. 



[ABSTRACT.] 



// Grnba. E tin fiume di frontiera tra il B.E.A. e la Somalia 

 Italiana Meridionale. Dalle sorgenti (Arussi) alia foce 

 (Oceano Indiano) v'hanno 1600 km. Del suo corso, in parte 



