14 
PACIFIC SCIENCE, Vol. V, January, 1951 
marked, easily recognized characters to those 
differing so slightly that only statistical ana- 
lyses of quantitative data will identify them. 
They are not frequent in occurrence, with 
the exception of a few which have been shown 
to be frequently mutating types (Collins, 
1936 ). The mutations discussed here have 
been collected over a period of 20 years or 
more and from among millions of normal 
plants. 
This variety is as stable genetically as are 
vegetatively propagated, highly heterozygous 
diploid varieties in general. Were this not 
true, the variety could not have been main- 
tained through this long period of time. 
Cayenne is not the single clone it probably 
was at the beginning. Now it is a collection 
of clones, all having the same general char- 
acters but usually differing in one or a few 
characters or degrees of expression of char- 
acters. The more obvious mutations and those 
too poorly adapted to survive in the general 
population have been and are being reduced 
to small percentages or eliminated. The re- 
maining population heterozygosity consists 
of minor character alterations which are car- 
ried along by asexual propagation in the 
general mass of cultivated plants. As examples 
of these latter clonal types, reference can be 
made to some of those listed in Table 1, such 
as the clone with less porous fruits, self- 
seedy types, low and high slip-producing 
forms, and increased amount of chlorophyll. 
As to their value to the organism (in a 
cultivated variety, positive value in horticul- 
ture) these somatic mutations follow the 
known pattern of randomly occurring muta- 
tions; the great majority are either detrimental 
or of no advantage to the organism. Only 
three of those which have been studied appear 
to have possible advantage in pineapple cul- 
ture, and only two of these, the wilt-resistant 
mutant and the high slip-producing type, are 
of possible importance. 
TETRAPLOID CAYENNE 
The pineapple normally has 50 chromo- 
somes in its somatic cells. This is considered 
to be the diploid number for the genus 
Ananas. However, tetraploid Cayenne plants 
having 100 chromosomes were obtained after 
treating shoot growing points with colchicine 
solution (Kerns and Collins, 1947). The im- 
mediate results from these treatments were 
various kinds of chimeras of diploid and tetra- 
ploid tissues, together with plants which 
either died early in growth or reverted to nor- 
mal diploid tissue throughout. 
By careful selection of buds from the tetra- 
ploid sectors of chimeras during several suc- 
cessive vegetative generations, constant new 
types which fall into the following three 
classes on the basis of the amount and loca- 
tion of tetraploid tissue were obtained. 
Class 1 was completely tetraploid. 
Class 2 was tetraploid except for a diploid 
epidermis. 
Class 3 was diploid except for a tetraploid 
epidermis. 
Classes 1 and 2 were alike in all visible 
characters. Class 3 was like the normal diploid 
in all visible characters. 
The tetraploid has been compared in Table 
4 with the diploid in a number of important 
characters. The fruit weight is less in the tetra- 
ploid and the fruit has fewer eyes than in the 
diploid. The average eye weight, however, is 
higher in the tetraploid, showing that the 
individual eyes of the tetraploid are larger. 
The Brix (dissolved solids including sugars) 
of the tetraploid fruit is lower than in the 
diploid fruit. The characters of fruit acidity, 
translucence, and vitamin C content are high- 
ly variable, so that no significant differences 
were obtained. These characters are readily 
altered by different environmental conditions. 
Tetraploid plants are taller than diploids, 
but they have fewer leaves and produce fewer 
slips. They do not differ in average leaf length, 
although the tetraploids have wider leaves. 
The tetraploids also have a higher percentage 
of water in the leaves and, as a consequence, 
a lower percentage of dry matter per unit 
weight of green leaf tissue. 
