genome analysis based on hybridization, cannot be con- 
sidered evidence against possible existence of true phylo- 
genetic relationships between these species. As discussed 
earlier, even in the case of the genus Coix, comparison 
of the chromosome morphology of the three species does 
not indicate the presence of the common genome demon- 
strated by intergenomic pairing of chromosomes in in- 
terspecific hybrids. 
Chromosomes of C. Lachryma-Jobi and maize exhibit 
a few similarities. They fall in approximately the same 
length range at pachytene (data from this study com- 
pared to measurements of maize chromosomes given in 
the publication by Rhoades, 1955) as well as at diakine- 
sis and metaphase I (Longley, 1941). Knobs, the sizes 
of which and positions on chromosomes vary in different 
populations, are present in both species. There is, how- 
ever, no evidence based on genome analysis to indicate 
that these similarities reflect true phylogenetic relation- 
ships. The many attempts made at producing viable 
hybrids between maize and Coix have so far met with 
failure (Mangelsdorf and Reeves, 1989: Venkateswarlu, 
1963). 
Summary 
Lengths, arm-ratios, and other morphological features 
of chromosomes at the pachytene stage of meiosis are 
reported for three species of Coix, namely, C. aquatica 
(2n=10), C. Lachryma-Jobi (2n=20), and C. gigantea 
(2n=18). The genome of C. aquatica is the longest of 
the three species and is about 40% longer than that of 
either of the other two species. When stained with 
acetocarmine the chromosomes of C. aquatica show con- 
spicuous differential staining into eu- and heteropyenotic 
regions. They also exhibit non-homologous association of 
centromeres and heteropyenotic regions. C. Lachryma- 
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