28 
BULLETIN Gi, HAWAII EXPERIMENT STATION 
The whipgraft method differs from that of the cleft-graft only in 
form of union and should receive the same care as the latter. The 
cut surfaces of stock and scion are beveled off to about an inch in 
length. Tongues are cut in these surfaces to aid in holding the 
united parts together. The union is then bound with raffia. The 
two kinds of grafted plants should be shaded in the slat propagation 
house for three or four days and then given full sunlight. The bind- 
ing should be removed in about a week's time, and as soon as the 
union seems to be thoroughly healed the plants should be set in their 
permanent place in the orchard. 
The object of the field experiment with large dioecious papaya 
plants was to determine the possibilities of changing the staminate, 
nonbearing plants 
into fruitful ones. 
The seedlings used 
were grown for the 
first six weeks in tin 
containers. They 
were then set in or- 
chard form on Sep- 
tember 15, 1920, and 
began to bloom in 
two and one-half 
months. Among 
these seedlings, 
Avhich were of stock 
that had been im- 
proved at the sta- 
tion by seed selec- 
tion for a number 
of generations, the 
male or staminate 
plants constituted 
36 per cent. A 
number of these 
were grafted in Jan- 
uary, 1921. At this 
time the seedlings 
had an average 
height of 4 feet, and 
a trunk diameter 
ranging from 2^2 
to 4 inches, measured 1 foot above the ground. The graft unions 
were made at various heights from 2 to 3 feet above the ground, the 
place of each being determined by the size of the individual scions 
provided for the work. Scions a foot or more in length were taken 
as lateral branches from good fruiting plants. These were difficult 
to obtain. However, such growth was obtained by topping back the 
parent plant, which resulted in a forced growth of lateral branches. 
The methods of grafting used were the saddle graft and the whip- 
graft. The former gave the best results, as the stock and the scion 
tend to make uniform growth all the way around the stem. Open- 
ings leading into the central cavity are sometimes formed in the 
Figure 28. — A papaya plant grown from a cutting some 2 
inches in diameter which rooted when set in soil of decom- 
posing volcanic cinders 
