Page:Popular Science Monthly Volume 60.djvu/399

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After the nut sprouts from the ground a rootlet starts from the young trunk a few inches above the soil and grows downward to the earth; then another and another starts out a little higher up, each growing down into the ground. As the tree increases PSM V60 D399 The spiny trunk of a bactris.pngFig. 5. The Spiny Trunk of a Bactris. in size these roots continue to grow outward and downward always at an angle that will most effectively brace the trunk. I have seen the roots starting from the trunk seven and a half feet from the ground.

Structure of the Trunk.—The structure of the palm trunk is always the same in that it is made of fibro-vascular or horny bundles and parenchyma or pith; as a rule, too, the horny bundles are grouped together near the surface of the trunk, while the central portion holds most of the pith. Seen in cross-section the palm trunk is very like the stalk of the Indian corn. There is, however, a marked variation among palms in the direction of these bundles through the stems, for in some they ascend the trunk in a vertical plane while in others they take a spiral direction, not keeping parallel with each other but crossing one another in a bewildering maze. As these hard bundles are what give strength and resistance to the palm trunk, it will be seen that the possibility of splitting some of the trunks must depend upon the direction of the fibro-vascular bundles. In the Iriartia or paxiuba the fibro-vascular bundles lie in a vertical plane and are parallel, so that a section of the trunk of this palm splits with ease, and for this reason it is extensively used for umbrella handles, walking canes and such like purposes. Some of the palm woods admit of a beautiful polish, PSM V60 D399 Roots of an ordinary palm.pngFig. 6. The Roots of an Ordinary Palm. and, in these cases, the winding directions of the bundles cause them to be cut off at various angles and render the ornamental pieces made of them very beautiful. The fibro-vascular bundles vary greatly in color in the different palm trunks, some of them being nearly white, others amber-colored, others black and still others dark brown; most of them have a waxy, horn-like luster, and all of them are, when mature, exceedingly hard.

The purely mechanical office which these fibro-vascular bundles perform is necessarily of the utmost importance in giving character and form to the trunk. They extend also from the trunks out into