COURSE OF THE BUNDLES IN THE STEM. 349 



with those of the outer, so that their outer portion falls between the latter, but their 

 number is not always the same as that of the outer series, one being left out (e. g. ^ in 

 the specimers at hand of Tladiantha). 



The bundles of both rings are, as far as investigated, bundles of the trace, which pass 

 downwards on the average through two internodes : it remains for further investigations 

 to ascertain their course exactly, a matter which is made very difficult by the early ap- 

 pearance of irregular transverse anastomosing bundles in the nodes. 



Of those Aniarantacex, which have been investigated, some, namely species of Celosia, 

 Gomphrena, Alternanthera, Froelichia, and Achyranthes, have the primary ring of 

 bundles, and pith cylinder (the latter without bundles), which are typical of the Dicoty- 

 ledons. In Amarantus^ caudatus, A. retroflexus, and Euxolus emarginatus A. Br. the 

 numerous (e.g. 11) bundles, which are arranged in the base of the leaf in a curved series 

 concave upwards, separate from one another in the node, taking however a steep down- 

 ward course : some form a ring with certain bundles, which descend from above, others 

 penetrate deeper into the pith. Thus there are formed within the ring of bundles 

 several irregular medullary rings, in which the bundles belonging to individual leaves 

 remain grouped together. The middle of the pith has no bundles. The median bundles 

 of each leaf-trace appear to penetrate deepest into the pith. Lower down the bundles 

 of one trace unite, after traversing several internodes separately. An accurate investi- 

 gation of their course remains still to be made. Slender specimens of Euxolus lividus 

 Moq. show similar, but simpler conditions. 



Phytolacca dioica has (according to Nageli, I.e. p. 118) three bundles of the trace for 

 each leaf. The two lateral ones descend in a radially perpendicular direction in the stem 

 between the pith and outer cortex ; they split first into two, then into several shanks, and 

 these together form the ring of bundles. The median bundle enters the pith, but hardly 

 deeper than i the radius of the pith, it there descends through 8-12 internodes, and then 

 again unites with the ring. It describes a curve convex inwards, the strongest curvature 

 of which is in its upper part : it reaches nearest to the middle of the pith in the 3rd and 

 4th internodes. The transverse section through a mature internode thus shows 8-13 

 bundles, which are free within the ring. 



The course of the bundles, which in the aerial stem of Podophyllum, Diphylleja, and 

 Leontice '^ are distributed in the transverse section throughout the pith, almost as in the 

 Monocotyledons, and of those which, in Papaver orientale (often also in P. somniferum), 

 in Actxa racemosa, Cimicifuga foetida, and species of Thalictrum, form an irregular 2- or 

 3-seriate zone round the pith, requires further investigation: it can hardly be doubted 

 that they belong to the leaf-trace. 



Further investigation must show whether the medullary bundles, which occur in Statice 

 or the Plumbagiiiefii^, belong to this series: I found no such bundles in the species of 

 Statice, Armeria, and Plumbago which I examined. 



Since P. Moldenhawer and E. Meyer it has been known that in the internodes of all 

 Piperaceai which have been investigated, with the exception of Verhuellia, there are 

 medullary bundles, usually arranged in a circle, within a ring of bundles, which in the 

 woody species (Pipereae) subsequently undergo secondary thickening. Rarely more than 

 one inner circle is present, e. g. in Peperomia variegata sometimes 2, in P. incana and 

 obtusifolia 3-4, in Piper geniculatum 2, in Artanthe cordifolia 4 *. The number of the 



' Link, Grundlehren der Anatotn. und Physiol, der Pflanzen, pp. 144, 148. — Unger, Dicotyle- 

 donenstamra, p. loS. 



^ C. H. Schultz, Vaisseaux du latex, &c., Mem. pres. Acad. d. Sciences, VII (1841). — Sanio, 

 /. c. p. 230. 



^ Russow, Vergl. Unters. p. 15,3.— Schwendener, Mech. Princip. p. 143. 



* P. Moldenhawer, Beitr. p. 5. — E. Meyer, De Houttaynia et Saurureis, p. 39 Unger, Bau, 



&c. des Dicotyledonenstammes, p. 68, &c. — Karsten, Veget. Org. d. Palmen, I.e. p. 148. — C. de 

 CandoUe, Memoire sur la famille des Piperacees, Mem. Soc. phys. de Geneve, Taf. XVIII. p. 2. — 



