and Galinat, 1964) and their backcross progenies (Chag- 
anti, 1964). The objective of this study was to score the 
frequency of associations which are a consequence of ef- 
fective synapsis (synapsis followed by exchange, reflected 
as chiasmatic associations at metaphase) and homologous 
or homeologous synapsis in haploid maize (reflected as 
side-by-side associations at metaphase, Person, 1955: 
Riley and Chapman, 1957), in the haploid genom of 
Tripsacum and in the F; maize-Tripsacum hybrid. If the 
pairing frequency in one or both the species or their 
sum is equal to or greater than that of the hybrid, then 
most of the pairing in the hybrid would be autosyndetic 
and not reflective of intragenomic affinities. If, on the 
other hand, the pairing in the hybrid is higher than that 
of the parents individually or even that of their sum, 
then such an increase in pairing could only result from 
some intragenomic or allosynditic associations (Riley and 
Chapman, 1957). 
The haploid maize used for this type of comparison 
was found in the backcross progeny of a triploid hybrid 
of maize and T7ipsacum floridanum. Although no hap- 
loid 'Tripsacum plants as such were available or have ever 
been discovered, the essential information for our pur- 
poses was obtained from observations made on a haploid 
genom of Tripsacum isolated within a triploid hybrid 
which also contained two genoms of maize in each cell. 
Since the two genoms of maize pair with each other 
rather than compete with the Tripsacum chromosomes, 
any synaptic relationships within the Tripsacum genom 
are expressed, except when confused by rare but apparent 
maize-'l'ripsacum interchanges which occurred in the 
parental F; hybrid. Furthermore, any other exchanges 
between the non-homologous Tripsacum chromosomes 
occurring in the F; hybrid will be apparent (if the ex- 
change chromatids are transmitted to the egg develop- 
[ 308 | 
