COVRSE OF THE BUNDLES. 



233 



furrow of the stem. In the thick roots of the Pandaneae and the genus of Palms, 

 Iriartea, there are found a number of parallel bundles, which converge at the growing- 

 point : as will be mentioned in Sect. 108, it may be doubted whether these should be 

 called parts of one very large divided bundle, or so many individual bundles. The 

 tuberous lateral roots of the Ophrydese, of Dioscorea Batatas, and of Sedum Tele- 

 phium ', are on the other hand traversed by numerous separate bundles which 

 converge towards the apex, and are finally united into a short terminal portion. 

 In the undivided tubers of Ophrydese they diverge from the point of insertion to the 

 broadest transverse zone, and from thence towards the apex they curve and converge, 

 and unite there into a single short apex, which ends blindly. During their course the 

 bundles, especially the peripheral ones, are united here and there by anastomosing 

 branches meeting the bundles at an acute angle. The lateral roots of the above 

 species of Sedum, which require further investigation, appear to behave in a similar 

 manner, but the anastomoses are absent, and the terminal point is more elongated. 

 The thick cylindrical adventitious roots of Dioscorea Batatas, the development of 

 which also requires further investigation, are traversed throughout their length by 

 very numerous bundles : these are irregularly distributed over the whole transverse 

 section, have a sinuous course, and are connected on all sides by anastomoses. 



b. Course of bundles in the individual leafy stem ^. 



Sect. 60. The bundles, which traverse the stem, are separable according to 

 their course into two categories: firstly, such as always remain in the stem and 

 grow acropetally with it: they may either have no direct connection with the 

 bundles of the leaves, or the latter may be attached laterally to them : these are 

 the cauline bundles, which belong only to the stem : secondly, the bundles common 

 to stem and leaf, which run for a certain distance in the stem, and then enter a leaf, 

 and thus belong in one part of their course to the stem, in another part to the leaf. 



A stem may contain only cauline, or only common bundles, or both. 



The direction of the course of the bundles follows generally the longitudinal 

 axis- of the stem : it is only in the nodes, and in some unimportant connecting 

 branches, that the direction is exactly transverse. During this for the most part 

 longitudinal course, their direction with relation to the plane of the surface, which 

 may be provisionally considered as flat, and to that of a radial longitudinal section 

 varies; a bundle may run perpendicularly or obliquely relatively to both; that is, it 

 may be radially-perpendicular and radially-oblique, tangentially-perpendicular and tan- 

 gentially-oblique. By combination of these conditions, curved, ^'-shaped, and spiral 

 arrangements may result. 



After traversing a certain distance, a bundle may connect itself with another 

 to form a single one. There are accordingly distinguished separate- or individual- 

 bundles, and united bundles. 



1 Irmisch, Botan. Zeitg. 1855, p. 253.— Henry, Verhandl. Naturwiss. Vereins. f. Rheinl. und 

 Westf. i860. 



= Von Mohl, Palmarura structura, Monachii, 1831.— Hanstein, in Pringsheim's Jahrb. I. p. 233. 

 — Nageli, Zeitschr. f. Wiss. Bot. Heft 3 and 4, p. 129.— Beitr. •.. Wissensoh. Bot. I. 



