January, 1909.] 



33 



Edible Froducis. 



been the constant abandonment of 

 plats of cultivated land and the making 

 of new "caingins" or clearings for 

 temporary use. Chemical analyses do 

 not at all support the view that manioc 

 is a hard crop on the soil. The total 

 ash in the roots is commonly less than 

 2 per cent, of the dry weight, and the 

 nitrogen hardly more than 0*5 per cent. 

 Manioc does use nitrogen in the forma- 

 tion of hydrocyanic acid, beside in the 

 ways common to mosc plants, and 

 may therefore exhaust this food dispro- 

 portionately. This danger can be avoid- 

 ed by raising a leguminous crop with 

 the manioc or alternating with it. The 

 most promising leguminous crop here is 

 the mongo. Unless the soil is rich in 

 lime, the addition of this cheap food will 

 be good for both the mongo and manioc. 



Enemies. 



A scale in Africa causes yellow spots 

 on the leaves and leaf-minor lives in 

 them, but neither causes appreciable 

 damage. The same is true of insects 

 which occasionally gnaw them. Old 

 roots left in the ground in the Philip- 

 pines are often chambered or consumed 

 by insects, but young or fresh roots are 

 never attacked. 



Leaf-spot fungi occur in the Malay 

 States, Africa, and America, but no- 

 where do appreciable damage. The only 

 known serious disease of manioc is a 

 leaf curl in East Africa, called by the 

 natives "maratschi." It is a communi- 

 cable disease, but no micro-organism is 

 known to cause it. No variety of manioc 

 is free from it- A Madagascar variety 

 called Mpesazi, is the least generally 

 attacked. A sound plant of this variety 

 twelve months old may have 12 kilograms 

 of rooots, but the average yield of 

 thirteen plants with the leaf-curl was 

 only 0-41 kilogram. 



No disease of manioc is known in 

 the Philippines, Their most dangerous 

 enemy here is the hog- Wild hogs do 

 considerable mischief when they get 

 access to manioc, but they of course can 

 be kept out by good fencing. 



Culture. 



Knowledge of what is really best in 

 the culture of manioc is very limited, 

 the plant never having received a frac- 

 tion of the study which has been 

 bestowed on all the important crops of 

 temperate lands. On manioc we have 

 for the most part only scattered observa- 

 tions, and these are not always too 

 reliable. In the equatorial belt, where 

 manioc thrives best, the most usual 

 treatment of it is the most complete 

 neglect. The only attention it usually 

 receives in the Philippines is sticking 



the cuttings into the ground and digging 

 out the roots ; and in parts of India, 

 Africa, and South America it receives 

 no more care. The most careful study 

 has been given it in Florida and Jamaica ; 

 in the former all the conditions are very 

 different from those here, and in th6 

 latter the subject most studied has been 

 the selection of varieties. 



Manioc is in practice always reproduc- 

 ed by etem cuttings. Seeds are used in 

 the Government work in the United 

 States in attempts to secure new and 

 sweeter varieties, and in German East 

 Africa in attempts to secure immunity 

 from disease. So far as limited and 

 unsatisfactory experiments show, the 

 seedlings are likely to have sweeter 

 roots than their jjarents. However, in 

 Paraguay the seed of the sweet culti- 

 vated varieties is said to be very 

 unreliable and likely to produce poison- 

 ous roots. The stems will grow if 

 used as soon as cut and are presumably 

 most vigorous then ; but they have 

 stood shipment from Jamaica to India, 

 and in Paraguay have been kept alive 

 through six months of hot weather, 

 provided the epidermis was not bruised 

 or broken and they were kept dry. 



Only sound stems of sound plants 

 should be used. Cuttings 10 to 20 

 centimeters long will produce thrifty 

 plants. Some writers advocate the use 

 of longer ones, and it may be that their 

 use where there is plenty of material for 

 propagation will give the plants a 

 stronger start. The cuttings are buried 

 horizontally in some places, placed erect 

 with the lower end in the ground in 

 others, and planted obliquely in still 

 others ; they grow everywhere. The 

 crop will perhaps be more easily har- 

 vested if the cutting is not erect. If it 

 is erect it is advisable to plant in the 

 ground the original lower end, so that 

 the polarity of the cutting will not have 

 to be overcome when it begins to grow. 



Statements as to the proper distance 

 between plants differ widely, and this 

 depends of course upon the soil and 

 climate, and upon the natural growth 

 of the variety planted. On good soil a 

 distance of one meter in each direction 

 can be recommended for the Philippine 

 variety ; this puts 10,000 plants on one 

 hectare of even ground. If more room 

 for cultivation in one direction is desired, 

 the same stand can be obtained by putting 

 the rows 125 centimeters apart and the 

 cuttings 80 centimeters apart in the rows. 

 A somewhat more ample spacing is better, 

 if a short-lived catch crop is interplanted. 

 Some writers condemn the use of any 

 other crops with manioc, but it seems to 

 me that if well chosen they have decided 



