1916] HOFFSTADT— PIPER METHYSTICUM 129 



stem (fig. 20). In two cases it was observed that the branch did 

 not develop in the axil of a leaf where only the blade was developed 

 (fig. 21), which was due probably to the pressure caused by the 

 enveloping sheaths of the preceding leaves. 



Piper umbellatum 



The stem of Piper umbellatum is not essentially different from 

 that of Piper methysticiim. At maturity it has only one ring of 

 pith bundles. The bundles, instead of traversing two nodes as 

 internal bundles before fusing with the next group, traverse but 

 one (fig. 22). The young plants are covered with hairs, both uni- 

 cellular and multicellular. The number of leaf traces is 7-9. In 

 the young stem there is an abundance of mucilage scattered in all 

 regions. In the old stem a single mucilage canal appears in the 

 center, which is continuous through the nodes and in the branches; 

 Van Tieghem found none that was continuous through the nodes 

 (fig- 23). 



Summary 



1. The stem of Piper methysticiim 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 periph- 

 eral 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. 



