spread pachytene chromosomes (Plate LIX, a, b). All 
the chromosomes of this species, Just as in the case of 
those of C. aquatica and C. Lachryma-Joln, show differ- 
ential staining into eu- and heteropycnotic regions, the 
latter being present in the proximal as well as interstitial 
regions of chromosome arms. Furthermore, the chromo- 
some arms terminate in deep staining chromomeres. An 
idiogram constructed on the basis of mean values of at 
least ten measurements of lengths and calculation of arm 
ratios for each chromosome is presented in Plate LN 
(see Table I1). The eighth longest chromosome of the 
complement has the nucleolus organizer situated almost 
terminally on the entirely heteropyecnotic short arm 
(Plate LN). 
Discussion 
Variation in chromosome morphology and knob numbers 
in C. Lachryma-Jobi: The species of Coix are predomi- 
nantly outbreeding. Four to six varieties have been 
recognized in C. Lachryma-Jobi based on morphological 
features of the fruit case (Mimeur, 1951; Bor, 1960). 
The varieties interbreed readily if grown together and 
allowed to open pollinate and their identity is lost within 
a few generations. Hence, the varietal differences are 
based on gene mutations, and the varieties arose through 
geographic isolation of populations or through selection 
by man. The variation observed at the population level 
in the chromosome phenotype: namely, the degree of 
heteropyenosis in chromosome arms and the sizes and 
numbers of knobs; can also be considered part of the 
same evolutionary processes that lead to varietal deline- 
ation. A detailed study of the variation of the chromo- 
some phenotype has not yet been accomplished, but 
available information points to existence of a considerable 
amount of it. The fact that, in one of the populations 
[ 212] 
