PN-5218 



Figure 4. — Petiole and nodal structure of D. rotundata. 



never brightly colored by anthocyanin. Anthocyanin coloration is 

 a varietal trait. The petioles are usually enlarged at the two ex- 

 tremes (fig. 4) and may be striated. 



The flowers of D. rotiindata and D. cayenensis are usually 

 produced early during the vegetative cycle. In Ibadan, Nigeria, 

 most D. rotundata and D. cayenensis cultivars usually start flower- 

 ing in June. The percentage of flowering plants in a yam field 

 is low, and among plants that flower, there is a preponderance of 

 male over female plants. D. cayenensis usually produces male 

 flowers and seldom female flowers. D. rotundata usually produces 

 male and female flowers on separate plants. Sadik and Okereke 

 (27) reported plants that produce either male, female, or complete 

 flowers on the same plant. 



The male flowers of D. rotundata are 1 to 3 millimeters in 

 diameter, sessile, and borne on spikes subtended by small bracts. 

 The perianth is slightly connate at the base and consists of three 

 light-green sepals and a corolla of three light-yellow petals. The 

 androecium consists of two whorls of three stamens each. Anthers 



7 



