4 BULLETIN 55, HAWAII EXPERIMENT STATION 
though somewhat fibrous, are coarse in structure and often contain 
as much as 85 per cent water (16, p. IT). The trunk and large leaves 
present an ornamental appearance and the flowers and fruit par- 
ticularly are interesting botanically. 
ROOTS 
The root system consists of two sets of roots, the horizontal and 
the vertical ; the former, which is the superior, radiates from around 
the bulb, whereas the latter extends downward from the base. The 
main roots are tough and cordlike and of nearly uniform thickness 
throughout, possessing numerous short, threadlike secondary roots 
or rootlets growing out at right angles. Both main and secondary 
roots bear numerous root hairs, or feeders, which absorb liquid plant 
food from the soil. The food passes along the fibrovascular system 
of cells of the roots, bulb, and stems, to the leaves. Investigation 
shows that the banana roots, unlike those of many other plants, can 
not adapt themselves to adverse conditions, such as sour or heavy 
soil. The distance to which they extend depends largely upon the 
nature of the soil. Under favorable conditions the horizontal roots 
may be found at a depth of 6 inches to 2 feet, and the vertical roots 
6 inches to 6 feet, both growing at the rate of 2 feet per month. 
STEM 
The true stem is the underground " bulb," morphologically known 
as a tuberous rhizome, wherein is stored the starchy plant food used 
in connection with the central bud, root, and sucker-bud-producing 
tissue. The suckers rise from this tissue as additional trunks of the 
plant group. The trunk consists of a cylinder composed of coarsely 
constructed concentric layers, each of which is the base of a leaf- 
stalk. Combined, these layers protect the younger leaves and the 
flowering stalk. The plant food is used chiefly in the production of 
suckers and the growth of the fruit. The production of too many 
suckers results in poorly developed fruit. A sucker may be consid- 
ered a plant when it has developed to a size with sufficient roots to 
maintain its own growth fully. 
LEAVES 
The leaves of the banana plant, consisting of leafstalk and blade, 
vary in number from 8 to 20 or more, depending upon the vigor 
of the plant. Normally, they are 8 to 12 feet long and 2 feet or more 
wide. Prior to expanding, the young leaf is cylindrically rolled on 
itself, being closed at the tip, possibly to prevent water from entering 
the center of the trunk where the blossom bud is forming. The 
exposed portion of the petiole or leafstalk, which varies from one 
to several feet long, is almost cylindrical, its raised edges forming a 
distinct trough above. The leaves are so arranged as to adapt them- 
selves to weather conditions. When the sun's rays are perpendicular 
and too intense, the blade collapses, the under surfaces containing 
the pores (stomata) coming together and thus protecting the plant 
against too great evaporation. In wet and moderately cool weather 
when growing conditions are very favorable the edges of the blade 
curve upward, permitting increased evaporation, which is necessary 
