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 filled 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. 
wo 20. 45 = », Manure without nitrogen. 
” 3rd ”) ” » ” ” phosphoric acid. 
ge ALD 5 ss 3 if », potash. 
” 5th ” ” yy ” 49 lime. 
i Oth; 3 5 i. ,, magnesia. 
” 7th ” 3 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. ‘he 
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. Natto Mazzoccu1 ALEMANNI. 
[ABSTRACT. | 
Il Ginba.—E un fiume di frontiera tra il B.E.A. e la Somalia 
Italiana Meridionale. Dalle sorgenti (Arussi) alla foce 
(Oceano Indiano) v’hanno 1600 km. Del suo corso, in parte 
