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PRIMARY ARRANGEMENT OF TISSUES. 



bundles, both of the inner and outer circle, varies, at least in many species, in the suc- 

 cessive internodes of the same shoot. They run perpendicularly down the individual 

 internode. In most species transverse anastomosis in the node makes it difficult to 

 follow their further course. Most recent authors have arrived at the result that the 

 bundles are partly common, partly, and especially the inner ones, cauline: the in- 

 florescence certainly contains cauline bundles. Karsten alone, in the year 1847, ex- 

 pressed another view for the Piperaceae, according to which all the bundles are bundles of 

 the leaf-trace : this view is confirmed and generalised by the more thorough investiga- 

 tions of Weiss. The latter can only be epitomised here, reference being given to the 

 original work, since the latter only appeared after this book had begun to pass through 



the press. 



Peperomia galioides shows the course most clearly. The leaves are arranged in 

 whorls of five, each has a single bundle. The bundles enter the node in the outer circle, 

 and pass down in it through one internode: they then curve inwards, and, forming the 

 inner circle, pass down the second internode : in the node below the latter they insert 

 themselves on the bundles of the next higher whorl, which here curve into the pith. 

 The transverse section through the internode shows two concentric series of five bundles 

 each. 



P. brachyphylla has decussating whorls of two leaves each. Each leaf contains three 

 bundles, one median and two lateral. ' The median bundles run in the peripheral circle 

 through two internodes, then turn inwards, and, after a further course in the pith through 

 one internode, insert themselves with their tapering ends on a medullary bundle. All 

 lateral bundles of the trace run through one internode in the peripheral circle, then 

 curving in the next lower internode into the pith, they run further in the pith through 

 one internode, and insert themselves, also with tapering ends, on the medullary bundles of 

 the third internode.' In each node accordingly six bundles pass inwards; in the pith of 

 the internode however there are only four: certain bundles must therefore unite on enter- 

 ing the pith. Weiss found the course similar, but more complicated and less regular, in 

 P. rubella, and in P. variegata and incana, which have alternating leaves : of these the 

 former has a leaf-trace of twelve bundles, the latter of seven. 



Weiss, in common with Karsten, found in the woody Piperaces (Piper, Artanthe, 

 species of Chavica) that the bundles of the many-bundled leaf-trace, which embraces the 

 stem, descend, where there are one or two medullary circles, through at least one internode 

 in the peripheral circle, then curving into the pith, they traverse a second internode in the 

 medullary circle, and finally insert themselves on medullary bundles of a lower internode. 

 On passing from the outer to the inner circle two or three bundles may unite, and the 

 number of the medullary bundles may thus vary with little regularity in the successive 

 internodes. Where there are more than two circles (Artanthe cordifolia) the medullary 

 bundles traverse at least two internodes. 



It is instructive that the course of the vascular bundles in the Piperacese closely re- 

 sembles that of the Commelineae (§ 69). 



2. A// hiindks belong to the leaf -trace. After entering the stem they pass over 

 into a network of bundles, which bratiches in-egtdarly on all sides. To this series 

 belong the Nymphaeacese, Gunneracese, Primula Auricula, and its nearest allies, 

 perhaps also many Balanophorese. In the first three groups a definite number of 

 bundles are seen to enter the stem from each leaf, and immediately after entering 

 they pass over into a network of bundles, which are irregularly connected both 

 in the direction of the surface of the stem, and also in radial planes by oblique and 



vSanio, Botan. Zeitg. 1864, p. 193. — F. Schmitz, das Fibi ovasalsystcm d. Piperacecn, Diss. Essen, 

 187 1. — J. Weiss, Wachsthumsvcrh.. &c. d. Piperacten, Flora, 1S76. 



