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of the hull causes it to shrink and eventually to split lengthwise at some point.
Further shrinkage often follows until it covers only a small portion of the nut
surface, and the nut falls to the ground. Within the tough, moderately thick
shell is a round white kernel of delicious taste, either fresh or roasted. It
constitutes about 30 to 40% by weight of the whole nut and contains from 60 to
80% oil and 8 to 10% protein. The nuts are very difficult to crack by hand
without mashing the kernel, but special machinery has been developed to handle
this problem commercially.

The smooth-shelled species, M. integrifolia, above described is the one
grown almost exclusively in Hawaii and California. Unfortunately, the botanical
name has been changed in recent years. Formerly it was called M. ternifolia
var. integrifolia. A very close species, M. tetraphylla, is called the rough-
shelled macadamia because its nuts, broadly elliptical rather than round, have
slightly bumpy surfaces. This species is distinguished, as the botanical indicates,
by having normally 4 leaves at each node; the leaves being longer than in
M. integrifolia and heavily spiny along the margins. There is a blooming period
in spring only. The nuts are as large as, or larger than, those of the smooth-
shelled type but are considered less satisfactory for processing in Hawaii, in
part because of thicker shells. In Australia the rough-shelled species is more
grown than the other.

A number of named varieties have been selected and propagated in Hawaii,
and these are being tested in California and Florida. Selection was made for
yield primarily, but also for nuts of fairly large average size and thinner than
average shells. Clonal varieties are being grown in Australia, also. Grafted
trees of the best adapted varieties usually have yields 3 to 5 times the average
as many
Propagation may be done by either side-for veneer-grafting on seedling stocks.
Seeds should be less than 4 months old for good viability. It is best to plant them