ent insects are suspected to pollinate the flowers, and hand 

 pollination is also effective (18). 



The fruit is a three-winged capsule, with one or two seeds in 

 each wing. The seed is flat, somewhat rectangular in shape, and 

 consists of a discoidal embryo and endosperm surrounded by a 

 membranous wing. 



The tubers are produced as terminal enlargements of stolons 

 (runners) from the primary nodal complex (5). These runners 

 are produced in successive rings from the crown, each ring higher 

 than the previous ring, and are of stem origin. Although they 

 resemble roots and are often covered with adventitious fibrous 

 roots, they do not have the internal structure of roots. Runners 

 with tubers vary from about 5 to 50 per plant. The tubers may be 

 placed at various distances (0 to 75 centimeters) from the crown of 

 the plant. In a good variety, it is convenient, if not almost essential, 

 to have the tubers arranged compactly around the crown on short 

 stolons. 



Tubers vary in shape. A common form is the spherical or 

 somewhat club-shaped tuber (fig. 5) . The tuber can be compressed 

 and somewhat discoidal, or shaped like a horsehoof (fig. 6). Those 

 of other varieties are often elongated and narrow (fig. 7). The 

 form of the tuber varies somewhat on a single plant because of the 

 degree of enlargement that occurs and because of the malforma- 

 tions caused by hard ground or obstacles in the soil. The surface 

 usually can be covered by a few fibrous roots. Some typical varia- 

 tions of tubers among the seedlings in Guadeloupe are shown in 

 figure 8. 



The cortex of the tuber is thin and smooth, with a few elon- 

 gated cracks. The internal color offer varies from white because of 

 the presence of yellow (carotenoid) and purple (anthocyanin) pig- 

 ments- Deeply purple-fleshed varieties are known and are some- 

 times especially appreciated. A wide range of intermediate and 

 compound color forms has been seen, including tubers with 

 brownish flesh and chimeras with white and purple sectors. 



Cytology 



The majority of the Dioscorea species of the New World are 

 tetraploids and hexaploids with 36 to 54 chromosomes (27). Ac- 

 cording to Henry (18), the chromosome number of D. trifida is 72, 

 although an unusual hermaphroditic plant with 81 chromosomes 

 was seen, and a nonf lowering plant contained only 54 chromosomes. 

 Observations in Guadeloupe revealed chromosome numbers of 18 

 (diploid), 36 (tetraploid) , and 54 (hexaploid). Henry found a dis- 

 tinct long chromosome in males and hermaphrodites, possibly a 



(Continued on page 10.) 



7 



