79 



I-IO acre in size could be planted out in April, 1906. Speaking 

 generally, the growth of these cassavas compares unfavourably 

 with that of our best native varieties of cassava and only 6 out of 

 the 26 varieties can be regarded as of any apparent value as starch 

 producers under the conditions obtaining at Hope. It is quite 

 possible that in the hills some of these varieties would flourish and 

 prove of real value to small cultivators. It is suggested that a stock 

 of these Colombian varieties should be offered to any branches of 

 the Agricultural Society in the mountain districts for trial by the 

 members. Two of the varieties can be considered as worthy of 

 serious attention as starch producers in the plains : "Miguela" and 

 "Negrita 15." The former gave a return of 13-3 tons tubers and 

 over 9,000 lbs. starch per acre, while the latter yielded 11-4 tons 

 of tubers and 7,863 lbs. starch. 



^ At the same time a native variety of sweet cassava, " Luana 

 Sweet," has given under the same conditions the same yield of 

 tubers as " Miguela" with a higher starch content amounting to 

 10,015 lbs. per acre and the victory rests with the local variety in 

 the competition as to starch production. It is possible that " Mi- 

 guela" and "Negrita 15" will improve as they become more accli- 

 matised and they must be regarded as valuable varieties. 



Hydrocyanic Acid Content. 



These Colombian varieties, however, were not imported as 

 starch-producers but as wholesome food free from risk of poison- 

 ing by hydrocyanic acid. As grown in Colombia these cassavas 

 are stated to be quite non-poisonous. After a year's growth in the 

 Liguanea plains of Jamaica they were tested in this laboratory and 

 14 varieties were found to contain on the average .0034 per cent, 

 of hydrocyanic acid in the whole tubers.* After a further period 

 of four years growth in the same changed locality the hydrocyanic 

 acid content rose to .0124 per cent, or practically four fold. 



This was predicted by Messrs. J. Shore and J. T. Palache from 

 their knowledge and experience of growing cassavas from higher 

 elevations at a lower. The increase is mainly due to the cortex. 

 This averages .0649 per cent, hydrocyanic acid while the edible 

 portion only contains .0026 per cent. Of the total percentage of 

 .0124 hydrocyanic acid, 81 per cent, or .0100 exists in the cortex 

 and only 19 per cent., on the average, is contained in the edible 

 portion. 



According to Carmody's rule, in bitter cassavas the hydro- 

 cyanic acid is almost equally distributed throughout the cortex 

 and interior of the tubers, while with sweet cassavas the -greater 

 proportion of poison exists in the cortex. This is well borne out 

 by all these cassavas except two, " Palo Verde" and " Cajon 

 Amarilla" both of which from the distribution of hydrocyanic 

 acid should be "bitter" cassavas whereas they are to the taste 

 " sweet" and were found by actual experiment on four persons to 

 be non-poisonous. 



* The figures for hydrocyanic acid given on p. 37 of vol. I. should be doubled, 

 owing to an error in caculating the results of analysis. 



