The Cayenne Pineapple — Collins 
15 
The fruits are seedless, as are the diploids. 
The chromosomes perform regularly in germ- 
cell formation, and functional gametes are 
produced. 
Crosses between the Cayenne tetraploid 
and varietal hybrid tetraploids produce viable 
seed readily, but crossing with diploid forms 
produces very little seed; this is similar to the 
results obtained when varietal hybrid tetra- 
ploids are crossed with diploids. 
TABLE 4 
Comparison of the Fruit and Plant Characters 
IN THE Diploid and Tetraploid Cayenne 
CHARACTERS 
DIPLOID 
TETRAPLOID 
Fruit weight (lbs.) 
5.8 
4.0* 
Eye number 
140.4 
105.6* 
Eye weight (gm.) 
16.3 
16.8* 
Brix 
15.4 
13.8* 
Acidity (per cent) 
0.71 
0.86 
Vitamin C 
19.2 
20.8 
Translucence 
2.7 
2.3 
Plant height (cm.) 
28.1 
30.5* 
Number of active leaves. . . 
57.6 
44.2* 
Leaf length (cm.) 
65.0 
65.2 
Leaf width (cm.) 
5.4 
6.2* 
Percentage water in leaves 
81.8 
83.5* 
Percentage dry matter in 
leaves 
18.2 
16.5* 
Pollen grain diameter (mi- 
crons) 
47.0 
64.0* 
Stomata size (microns) .... 
22.0 
31.0* 
*Significant differences. 
In many plants, and particularly in orna- 
mentals, valuable horticultural characters are 
obtained by doubling of the chromosomes 
(Emsweller, 1948: 570). However, the tetra- 
ploid Cayenne is inferior to the diploid form 
in several important characters (Table 4). 
GENETIC NATURE OF CAYENNE 
The Cayenne pineapple normally has seed- 
less fruits, although it does produce normal 
germ cells. The seedlessness results from a 
condition known as self-incompatibility. 
Under these conditions the germ, or sex, cells 
of the same individual do not unite in ferti- 
lization to form embryos. Germ cells from 
two different varieties, Cayenne and Queen, 
for instance, are mutually compatible and 
seeds are produced following cross pollination 
between the varieties. 
Inasmuch as inbreeding is thus denied be- 
cause of self-incompatibility, the studies of 
the genetic nature of Cayenne have been con- 
ducted largely from the results of varietal 
crossings and from examination of the soma- 
tic mutations which have appeared in field 
populations. 
Cayenne has a diploid number of 50 chro- 
mosomes; in the somatic cells they appear 
slightly elongated or almond-shaped (Collins 
and Kerns, 1931: 140); in the germ cells, they 
are almost round. While the process of germ- 
cell production is usually normal, some ab- 
normalities occur. The most frequent ab- 
normality is the formations of germ cells 
containing 50 chromosomes, which is double 
the ordinary number of chromosomes in 
gametes. These appear in the mature sex cells 
as giant pollen grains and ovules. 
In crosses between Cayenne and other 
varieties, these giant germ cells give rise to 
occasional hybrids having 75 or 100 chromo- 
somes instead of the normal number of 50 
for this species. 
The number of these plants whose cells 
have 75 and 100 chromosomes is far below 
the expected number on the basis of the per- 
centage of 50-chromosome germ cells pro- 
duced. This shows that only a small propor- 
tion of the plant gametes function in ferti- 
lization and that selective fertilization in favor 
of the normal 25-chromosome gametes takes 
place. 
Hybrid populations resulting from crossing 
Cayenne with other varieties provide some 
information regarding the genotype or heredi- 
tary constitution of the Cayenne variety. 
The variety is heterozygous for many reces- 
sive and dominant genes. Table 5 gives some 
information on the genotype of Cayenne ob- 
tained from crossing with other varieties. 
INBREEDING IN CAYENNE 
In discussing the somatic mutations which 
have appeared, mention was made of the self- 
