Chromosome Numbers of Some Species of Pass /flora 
Occurring in Hawaii 1 
W. B. Storey 2 
INTRODUCTION 
Passiflora is a genus of approximately 
400 species of plants, mostly woody or herba- 
ceous vines. About 360 species are native to 
tropical and subtropical North and South 
America and adjacent islands. The remainder 
are indigenous to southeastern Asia, a num- 
ber of south Pacific islands, and Madagascar 
(Killip, 1938: 9). Man has been instru- 
mental in disseminating many of the species 
with edible fruits or with highly colored, at- 
tractive flowers, and representatives of the 
genus are now to be found in most tropical 
lands throughout the world. 
Several species of Passiflora have been in- 
troduced into the Hawaiian Islands for culti- 
vation for their edible fruits (Pope, 1935). 
Additional species have been introduced for 
growing as garden ornamentals. A number 
of species, both edible and ornamental, have 
escaped from cultivation and are now to be 
found in a naturalized wild state along way- 
sides, on waste lands, and in lower forest 
regions (Pope, 1929: 149). A total of 22 
species has recently been reported as occur- 
ring in Hawaii (Neal, 1948: 522-525). 
A number of edible species, of which P. 
edulis is the most important, are cultivated 
as commercial crops in Australia, New Zea- 
land, and South Africa, where extensive use 
is made of the fruit. Their culture is prac- 
ticed to a lesser degree in various other trop 
ical countries, and in Florida, California, and 
1 Published with the approval of the Director of 
the University of Hawaii Agricultural Experiment 
Station as Technical Paper No. 180. 
2 Department of Horticulture, University of Ha- 
waii Agricultural Experiment Station. Manuscript 
received May 24, 1949. 
Hawaii. Numerous ornamental species and 
species-hybrids constitute an important item 
in the plant nursery business in the United 
States and elsewhere. 
Nurserymen have enjoyed some success in 
producing interspecific hybrid varieties for 
the floricultural trade. Fruit breeders, on 
the other hand, have had little or no success 
in attempts to improve upon existing edible 
types through interspecific hybridization, 
largely because of hybrid sterility. 
Cytological studies of plants often serve as 
a useful adjunct to plant breeding problems. 
Chromosome numbers and chromosome be- 
havior frequently indicate origins of species 
and relationships between species, and pro- 
vide clues as to which species are most likely 
to be compatible upon crossing. Despite the 
amount of breeding which has been done 
among species of Passiflora , in Hawaii and 
elsewhere, the genus is but poorly understood 
from the standpoint of cytology. The recently 
published Chromosome Atlas of Cultivated 
Plants lists the chromosome numbers of only 
seven species (Darlington and Janaki Am- 
mal, 1945: 114). 
This paper deals principally with reporting 
the chromosome numbers of additional spe- 
cies of Passiflora as well as of a number of 
botanical varieties and forms, interspecific 
hybrids, and an intraspecific chromosomal 
race. Notes on cytological behavior have 
been added where they might be helpful in 
clarifying origins or relationships. 
MATERIALS AND METHODS 
Chromosome numbers were determined 
for all species of Passiflora of which material 
for study could be obtained in Hawaii. Counts 
were made from root tips of seedling plants 
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