CHARACTERS IX AX UPLAXD-EGYPTIAX COTTOX HYBRID. 55 
In the cases of significant coherence in this hybrid, the smallness 
offthe coefficients of correlation, except where the relation is probably 
physical or physiological, indicates that the linkage is weak and that 
the percentage of crossing over is high. 
Of the 38 characters whose intercorrelations were determined in F 2 , 
37 are connected by coefficients of correlation amounting to at least 
three and one -half times the probable error. In view of the fact 
that the haploid number of chromosomes in Gossypium is probably 
not fewer than 20, it may appear surprising that so high a percentage 
of the characters are associated. It is probable, however, that more 
than two factors are involved in most of the characters here dealt with, 
the several factors for each character being in all likelihood distrib- 
uted in different chromosomes. 
It may be inferred from the results of this investigation that, 
although the data on correlation indicate relative freedom of recom- 
bination, the chances are heavily against the isolation and fixation 
of a productive type of cotton, combining the most desirable char- 
acters of both parents, from the segregation products of so wide a cross 
as that between upland and Egyptian. It is also evident that acciden- 
tal cross-pollination between these cottons can not but greatly impair 
both the uniformity and the fertility of either type. BothVf these 
conclusions are in line with the practical experience of cotton breeders. 
In roguing seed-increase fields of upland or of Egyptian cotton, 
the absence of characters definitely associated with the other type 
should not be regarded as proof that cross-pollination has not "oc- 
curred. It is advisable to remove all plants which show peculiar or 
abnormal characters on the suspicion that they are products of 
accidental hybridization. 
