1. The stem of Piper methysticum consists of two systems of bundles, peripheral and pith, the latter being in two rows. 2. The peripheral bundles are of two sizes: primary, the larger; secondary, the smaller. The latter are branches of the former. 3. The bundle type is collateral endarch. 4. The bundles are of foliar origin. 5. The bundles, after entering the stem, remain in the peripheral region through one internode and then traverse the pith for two internodes. 6. Both the peripheral and pith bundles show anastomoses. 7. The pericycle consists of only a few cells outside the bundles, which become lignified. 8. There is no differentiated endodermis. 9. The stem enlarges by cambial activity and divisions in the pith region. 10. An interfascicular cambium appears late in the internode and cuts off segments only on one side; it comes still later in the nodes. 11. Leaf traces are many. 12. The base of the leaf is sheathing and vernation is involute. 13. Buds vary in number and position. 14. Piper umbellatum differs from Piper methysticum in the following ways: (1) one ring of pith bundles only; (2) the mucilage canal runs through the center of stem and node; (3) the bundles run through one internode only in the periphery and one in the pith before fusing with those of the leaf above. 15. Both stems are packed, especially when young, with starch, piperin, and mucilage. 16. There are no growth rings.