COURSE OF THE BUNDLES IN THE STEM. 367 



bundles, or the above-mentioned isolated communications which occur within the 

 cyhnder. 



In most Scitamineae (Musaceae, Zingiberacese, Cannacese '), as far as descriptions 

 go, the vascular system in the cylinder is of the Palm type ; but outside the cylinder 

 there is a system of complete cortical vascular bundles. According to Wittmack's 

 description of Musa Ensete they are ' completely limited to the cortical layer, and 

 have a very sinuous, almost zigzag course, especially in the lower part. Owing to 

 their crowded arrangement and their frequent crossing, it was very rarely possible to 

 follow their traces far. But in favourable cases it appeared that they approach rather 

 near to the epidermis, and then proceed upwards parallel to the surface : but when- 

 ever they thus approach the base of a leaf, they curve inwards, and form anastomoses 

 with the chief vascular bundles (bundles of the trace), till finally they themselves 

 enter one of these leaf-bases, together with the large bundles which pass into it 

 from the interior of the stem. They here usually turn to the outer or inner wall of 

 the leaf-sheath, rarely they may be seen penetrating into the central regions, which 

 are traversed for the most part by the main bundles.' Wittmack found the same 

 arrangement in all the nine species of Musa investigated by him, in Strelitzia reginae 

 (weak), in the rhizome of Curcuma Zedoaria, in the flower-stalk of Phrynium viola- 

 ceum, and Calathea grandiflora : Meneghini found it previously in species of 

 Ravenala, Hedychium, and Canna. 



Sect. 68. As far as hitherto investigated, the single vascular bundle of the 

 cotyledon in the seedling of the Monocotyledons of the above types runs directly into 

 the axis of the main root, e. g. Allium Cepa ^ : or the cotyledon contains several 

 bundles, and these unite in the cotyledonary node, and then similarly pass into the 

 bundle of the root : e. g. Palms ". The bundles of the leaves which follow after the 

 cotyledons show the typical course, with such modifications as result from the small 

 number of bundles and the shortness of the internodes to be traversed. They unite 

 in the cotyledonary node with those of the cotyledon and of the root. 



. The elongated internode between the insertion of the scutellum and the first sheathing 

 leaf in the seedling of Zea Mais shows an abnormal arrangement. It contains a ringlike 

 mass of vascular tissue, which surrounds a wide pith : this ring is continued at the point 

 of insertion of the scutellum into the bundle of the first root. The annular mass originates 

 by the coalescence of the lower ends of the numerous bundles of the first foliage leaf- 

 traces with the trace of the first sheathing-leaf. The latter contains as a rule two bundles 

 situated right and left and in front of the median line. In the node they both bend in- 

 wards, and somewhat to the rear, and anastomose on reaching the node by means of a 

 curved connection : they then spread out and pass down in the ring. A branch goes also 

 from the curved connecting bundle perpendicularly downwards. The traces of the foliage- 

 leaves consist of many bundles, and are as wide as the whole circumference of the stem : 

 the lower ends of the lowest pass beneath the node of the sheathing-leaf between and 

 alongside of those of the latter, and with them they form, the ring. According to investi- 

 gations hitherto made — which require further completion— it appears that the individiial 



' Meneghini, /. c. — Wittmack, Musa Ensete, Halle (Linnsea), 1867. 

 " Sachs, Botan. Zeitg. 1863, Taf. III. 



-" Mohl, Palm. Struct, p. xliv. Tab. P.— Sachs, Botan. Zeitg. 1862, Taf. IX.— Compare also the 

 data on this point in van Tieghem, Symmetrie de Structure, &c., Ann. Sci. Nat. 5 ser. torn. XIII. 



