Higgins: Growing Melons on Trees 
attempt to enumerate the various 
species which have been crossed, since 
they have so far led to no commercial 
result. But it still seems possible that 
hybridization of the papaya with some 
more hardy species will produce a fruit 
which can be grown outside the tropics. 
Carica cundinamarcensis is one of the 
hardiest species. It stands considerable 
cold weather and bearsanacid fruit which 
is pleasant to the taste when properly 
cooked. If this could be combined 
with the papaya, a hardy form might 
be produced which would mature 
a good fruit in the southern United 
States, for example; while the true 
papaya can with difficulty be made to 
mature good fruit even in southern 
California, although it flourishes in 
southern Florida. 
IDEALS IN BREEDING THE PAPAYA 
There seems to be no good reason to 
doubt that it will be possible to breed 
a papaya combining at least many of 
the most desirable characters and to 
hold the variety reasonably stable by 
the same means as are employed in 
maintaining seed varieties of vegetables 
and garden flowers. This presupposes 
segregation or hand pollination in either 
case, the latter being the method which 
most breeders will be compelled to follow 
because of the proximity of other varie- 
ties over which they have no control. 
The simplicity of hand pollination in 
the papaya and the large number of 
seeds resulting from one operation 
render it a very practical means even 
for commercial seed production. 
It may be well to outline here some 
of the ideals which the breeder should 
have in mind in his search for Mende- 
lian characters which may be combined. 
1. Vigor of tree—It is important with 
the papaya, as with other species, to use 
vigorous individuals as parent stocks. 
2. Early and low fruiting habits— 
There is a wide variation in the plants 
in this respect, some producing no fruit 
on the first five or six feet of the stem, 
while others bear fruit which almost 
touches the soil. It is believed that this 
219 
character may be transmissble, and 
the advantage of early and low-bearing 
trees is obvious. 
3. Freedom from the branching 
habit—Trees that produce s«le branches 
freely require considerable pruning to 
prevent the numerous new shoots from 
taking the nourishment which should 
go to the fruit. 
4. Productivity but not excessive 
bearing—Trees that have long bare 
spaces on their stems and those whose 
fruits are so numerous as to crowd each 
other should be avoided in favor of such 
as have the fruits well spaced with just 
sufficient room to mature normally. 
5. Hermaphroditism—tThe reasons for 
preferring hermaphrodite stock have 
already been pointed out. It is essen- 
tial to a profitable industry that the 
number of “‘drone’’ male trees be kept 
very small. 
6. Suitable size in fruit—The size that 
will be most desirable will depend upon 
the purpose to which the variety is to 
be put. For home use or for the fresh 
fruit market the extremely large varie- 
ties are not popular, and the breeder of 
table varieties will not, therefore, at- 
tempt to originate such forms. On the 
other hand there is a place for these, if 
the fruit is to be grown as feed for poul- 
try or other live stock. For papain 
production, other things being equal, 
the large fruit would be best. 
7. Yield in papain*—Where the pro- 
duction of papain is made an industry 
there can be little doubt that the aver- 
age yield of this drug could be very 
greatly increased by judicious breeding. 
8. Uniformity of shape—The breeder 
must seek to establish varieties which 
will have reasonable uniformity of shape 
as well as symmetry and smoothness. 
It is not necessary that all varieties be 
alike, but there must be uniformity in 
pack. In breeding from hermaphrodite 
trees there will be a large number of pis- 
tillate trees in the offspring. Although 
the long form is not necessarily confined 
to the hermaphrodite tree, nevertheless 
pistillate trees do not usually yield fruit 
of this shape. For this reason the 
5 The juice of the fruit and sap of the papaya tree contain an active principle called papain, 
the effect of which is similar to that of pepsin. 
It is used medicinally, and also to clarify beer. 
Its digestive property is so great that raw meat placed in diluted juice will disappear 
altogether.—The Editor. 
