igi6] IIOFFSTADT— PIPER METHYSTICUM 121 



a short time xylem entirely surrounding phloem, and vice versa. 

 Bundles may join with either the phloem or xylem together. 

 They may He side by side and union may occur either in the xylem 

 or in the phloem. Not infrequently the xylem of two bundles 

 may unite, and the phloem of a third join the phloem of either of 

 the others. Strands become separated from bundles and several 

 of these may coalesce to make a bundle, or they may join with 

 other bundles. One often gets cross-sections and longitudinal 

 sections of the same bundle in the same section. 



The bundles in one internode are in the periphery, and through 

 the following two internodes are pith bundles. The position in 

 the pith often gives the appearance of two complete rings and one- 

 half of a third ring, when the number of bundles is large; but care- 

 ful study shows that there are really only two rings. The number 

 of bundles reaches 45-50 in the pith. 



Description of stem in detail 



As previously stated, the stem of Piper methysticum has two 

 sets of bundles which may be designated as the peripheral ring and 

 pith or medullary rings, two in number, and an irregular half- 

 ring which gives the appearance of a third ring at times. The 

 bundle type is open collateral endarch, oriented for the most 

 part in the usual manner. Sometimes, however, one finds the 

 protoxylem points appearing in reverse orientation (fig. 10, e-g). 

 Union is often incomplete and one finds double bundles persisting 

 in the internode, and these may be of two types. The xylem points 

 or the phloem points may be together (figs, n, 12). 



The peripheral ring of bundles is formed of two sizes: the 

 primary, those differentiated first; and the secondary, termed 

 supplementary by De Bray (3) (fig. 13). The secondary bundles 

 are branches of the primary bundles and he between them. 

 More than one primary bundle may contribute to a secondary one 

 (fig. 9); that is, two bundles may branch and the branches join. 

 The number of secondary bundles varies from none to 3, according 

 to the age and size of the stem. Near the tip there are none 

 (fig. 4), as observed by Schmitz (12). 



