COURSE OF THE BUNDLES IN TUB STEM. 25 f 



transverse anastomoses, the network being still further complicated by the insertion 

 of the bundles of roots and buds. Transverse and longitudinal sections through the 

 stem show ' irregularly scattered ' bundles, cut through in different directions ; the 

 former thus-remind one superficially of transverse sections of stems of Monocotyle- 

 dons, of which however only those of the Aroideae with irregular reticulate con- 

 nection of bundles can be more closely compared with them. 



The structure of species of Gunnera has been more exactly investigated by Reinke \ 

 In G. Chilensis Lam. (G. scabra R. B.) one bundle of the trace enters the short hypo- 

 cotyledonary stem from each cotyledon : the two unite, after a perpendicular course, to 

 form the axile root-bundle. The cotyledons are immediately followed by a pair of 

 almost opposite primordial leaves, which decussate with them : then come the further 

 leaves in spiral arrangement, all of them being separated from one another by extremely 

 , short internodes. From each of the primordial leaves three bundles, which unite in the 

 , cotyledonary node, enter the hypocotyledbnary stem : here the two united traces alter- 

 nate with those of the cotyledons, and unite with them lower down to form the axile 

 bundle. Exactly at their point of entry into the centre of the stem they are mutually 

 united by a horizontal bundle, parallel to the surface of the stem, and by one or a few, 

 •which traverse the middle of the stem obliquely. Branches from the latter pass to the 

 cotyledonary bundles. From each of the leaves, which next follow the two primordial 

 leaves, three, bundles enter the stem, and from the successively higher ones a larger 

 number (not exactly stated). Each successive leaf-trace resembles the first, inasmuch as 

 immediately on entering the stem it is connected with the network of bundles by con- 

 necting bundles in all directions; only the number of bundles of every sort and direction 

 increases in proportion as the axis of the seedling 2 mm. thick increases to the swollen 

 stem of 50 mm. thickness. The appearance of the bundles of all categories takes place 

 almost simultaneously. 



In conformation and structure the following species coincide with G. Chilensis : viz. 

 G. petaloidea, bracheata, insignis, commutata, peltata, manicata. G. perpensa L., to 

 which is allied G. macrophylla, has in its stem of i"™ in thickness, and with rather longer 

 internodes, for the most part bundles with a Jongitudinal course: most of these are united 

 into a hollow cylindrical net, within the parenchymatous cortex, and have transverse and 

 oblique connecting bundles, which traverse the pith. 



In the short internodes of the leafy stem of G. magellanica, which is 2-3 mm. thick, 

 3-4 vascular bundles run longitudinally; these are connected, dir&tly with one another, 

 by convergence, to form pointed elongated meshes, and also at the nodes they are united 

 by transverse anastomoses, at the points of entry of the three-bundled leaf-trace. The 

 elongated internodes of the stolons of this plant have usually only one concave band- 

 shaped axile bundle : sometimes this splits for a short distance into two. Finally the thin 

 stems of G. monoica and prorepens show in their internodes usually two bundles, which 

 are here and there united to a single one, into which the (one-bundled ?) leaf-traces run. 

 In the elongated internodes of the stolons they have one axile bundle. 



In Primula Auricula ' the one-bundled leaf-traces of the cotyledons and of the first 

 leaves unite, running almost horizontally into the middle of the stem, to form one axile 

 bundle which traverses it. The bundles which enter from the subsequent leaves run 

 for a distance — not defined by any constant number of internodes — side by side, and 

 then unite with one another, or with the axile bundle. As the plant grows stronger the 

 number of bundles entering one leaf increases to twenty, these pass obliquely down the 

 stem, and are here united by irregular and oblique branches and anastomoses, which run 



' Morphologische Abhandlungen, Leipzig, 1873, p. 47, Taf. 4-7. y 



'^ Vaupell, Ueber d. peripherische Wachsthum d. dicotyled. Rhizome, Leipzig, 1855.— Von 

 Kamienski, Zur Vergl. Anatomie d. Primeln, Diss. Strassburg, 1875. 



