PN-6371 



Figure 5. — Tubers of D. hispida covered with fibrous roots. 



deltoid, and tend to be covered with small, wiry roots. The flesh is white 

 to reddish and edible. The tuber is said to be perennial in the wild, an 

 unusual condition in edible species. The stems up to 10 centimeters in 

 diameter are round in cross section but sometimes prickled at the base 

 and with indistinct ridges. Upper stems are glabrous. The lower leaves 

 are alternate, but the upper leaves are opposite. Leaves are large, 

 cordate, or somewhat elliptic. The racemes of male flowers occur in 

 groups of one to four, about 4 centimeters long. The racemes of female 

 flowers are single or paired. 



D. transversa tubers are generally few (two to eight), linked by 

 short necks to a perennial woody head (fig. 7). They are more or less pear 

 shaped. The skin is whitish with numerous tiny weak rootlets. One to 

 several round or weakly ridged stems are produced, which turn to the 

 right. Prickles are rare. Leaves are alternate, triangular to cordate, 

 bright and smooth on the upper surface, purplish to brownish when 

 young. No bulbil or flower has been observed. 



Cytology 



Little information is available on the cytology of the minor species. 

 Chromosome numbers reported were summarized by Martin and Ortiz 

 (12). D. hispida is a tetraploid with 40 chromosomes. D. dumetorum 

 chromosomes counts are 36, 40, 45, 54. These are tetraploid, pentaploid, 

 and hexaploid numbers based on 9 or 10. D. rotundata and D. cayeyien- 



13 



