Edible Products. 



34 



[July, 1812. 



throw sprouts, but it is usually a waste 

 of mateiials to plant the distal 

 half of any ordinary yarn. Sections 

 or chunks of the cylindrical rooted 

 varieties weighing from 40 to ]00 grams 

 are regularly used in planting; if the 

 whole tuber is planted, especially if it 

 weigh more than one kilo, decay may set 

 in iiom some external injury, and before 

 the sprouts could develop sufficiently to 

 resist the attack, all of the material 

 might be consumed. 



In its habits of sprouting the ordinary 

 yam closely resembles the sweet potato, 

 which also is not a tuber, but a root. 

 The sprouts which from their uncommon 

 origin are called adventitious, may arise 

 fiom any point on the surface of the 

 root, though the tendency is confined 

 largely to the basal half. In this connec- 

 tion it may be remembered that the 

 cassava, which also stores up starch in a 

 true root, cannot be induced to send out 

 sprouts from even the basal end of the 

 root. 



Unlike most other root crops, growing 

 yams have a pronounced faculty of being 

 able to resist drought and the roots 

 alter harvesting may be kept for months 

 in a very dry atmosphere without injur- 

 ing their viability in the least ; in fact, 

 in some countries the roots, or the por- 

 tions of them to be used for planting, are 

 hung up in the shade, sometimes in the 

 roof of the dwelling house and at the 

 proper time for planting the roots begin 

 to send out reddish or purplish shoots, 

 thus advising the planter of the fact 

 that they consider it time to begin 

 another season's woik, so to speak. The 

 drought-resisting habit of tender-leaved 

 plants like the " Water " yams is rather 

 difficult to understand, since it appears 

 that there is no special physiological or 

 anatomical arrangemgnt in the leaf 

 surface or stem of the plant to prevent 

 evaporation of sap. The writer has 

 noticed in East Africa yam plants in 

 thriving condition with no indication 

 whatever of wilting during a prolonged 

 drought when all other crops and most 

 of the native plants were practically 

 dried up. This is still strange because 



the yam plant has no taproot and only a 

 very moderate number of feeding roots; 

 moreover, these latter do not seem to 

 penetrate deeply, as might be expected, 

 into the water-bearing strata of the 

 soil. 



Among the numerous characteristics 

 of the yams which render this crop of 

 plants worthy of special study and put 

 them in a sort of class by themselves in 

 plant societies, is the probably constant 

 feature of possessing in the raw state a 

 poisonous substance known as dioscor- 

 ein ; this little known vegetable alkaloid 

 has powerful effects upon animals or 

 man even when eaten in small quanti- 

 ties. Were it not for this fact the wild 

 yams would probably soon be extermin- 

 ated on account of the eagerness with 

 which the roots would be sought after 

 by wild pigs and other forest animals; 

 it is said that even poultry instinctively 

 recognize the dangerous nature of raw 

 yam roots and refuse to touch them 

 until cooked. Some yams possess a 

 peculiar, rather sickening odour, while 

 others have only a starchy smell like 

 that of a potato. All yams appear to 

 have, in addition to the starch, a gummy 

 or mucilaginous substance which is prob- 

 ably of a harmless nature. On account 

 of this gummy material, yams can never 

 be used as starch producers for the 

 reason that the gum prevents the set- 

 ting of the starch grains when the root 

 is ground and mixed with water ; neither 

 salt nor acids appear to be able to "cut" 

 this gum and therefore a mixture of 

 ground yam and water will ferment be- 

 fore settling. Upon cooking, however, 

 all traces of the alkaloid disappear and 

 the gum iLself is broken up so that at 

 least in the case of the principal yams- 

 even some of the " Water " type— they 

 become "mealy" like the very best 

 potatoes. Perhaps the whitest of all 

 root crops when cooked is the common 

 " Tugue ", a variety of yam which has 

 recently come to our notice and which 

 appears to beconfined to certain districts 

 in Luzon ; its white fecula is brilliant and 

 without the creamy tinge that most 

 potatoes have. A few yams, even when 

 b aked still remain somewhat watery, or 



