338 
to those employed in biometry to represent the continuous 
variations, that is to say, polygons of frequency or variation. 
The polygons of frequency have been drawn so that the 
frequencies represent the percentage of the different classes 
-per hundred or per thousand. 
The author also describes briefly the regions where the 
cottons which he has investigated are produced and the culti- 
vation experiments which have been made. He indicates the 
quotation obtained by each sample examined. 
The author gives, in a schedule, statistics relating to the 
export of cotton, the cultivated area under cotton, and the 
average production per hectare. 
The legislation relating to the encouragement of the produc- 
tion of cotton in the Portuguese Colonies is found at the end 
of the paper, which is illustrated by several photographs repre- 
senting cotton plantations and unginned cottons and twenty- 
two polygons of frequency. 
The Presipent: The subject which Professor Geraldes has 
brought to our notice is one which everyone who wishes to see 
the cotton cultivation of the world extended should read. Iam 
sure we shall read if and think over it, because it raises many 
important questions. He has, of course, only been able to 
give us a short summary of the elaborate and valuable paper 
which he has prepared for the Congress. 
GLI ASPETTI DELLA COTONICOLTURA DELL’ERITREA. 
Per Dott. Guipo Mancano.! 
[ ABsTRACct. ] 
La cotonicoltura assume nell’Eritrea tre forme ben distinte 
fra loro, ciascuna delle quali si svolge in una regione a sé, e 
porta ad organizzazione tecnica ed economica completamente 
diversa. I tre tipi sono particolarmente determinati dall’ 
origine delle acque di cui si vale la coltivazione; dimodoché 
si hanno colture che possono farsi con le sole acque di pioggia 
o con le sole alluvioni dei torrenti, opportunamente regolate. 
o con le pioggie e gli inondamenti insieme. La coltura bene- 
ficata dalle sole pioggie deve limitarsi a quelle zone che per 
il loro rilievo o per la lontananza da corsi di acqua non possono 
consentire la grande coltura irrigua in nessuna delle sue 
forme. Tali zone sono quelle del mezzopiano  sud-occi- 
dentale e, in parte, quelle del bassopiano verso i fiumi Gasc 
e Setit. Le varieta di cotone che possono esservi coltivate 
sono quelle a breve ciclo o quelle a tipo legnoso perenne. 
‘ Read by Dr, Oberto Manetti. 
