ANOMALOUS THICKENING IN DICOTYLEDONS AND GVMNOSPERMS. 603 



the radial bands of parenchyma of the highly parenchymatous wood, which extend 

 from the pith, the consequent splitting and disrupture first of the medullary sheatli, 

 then of the outer regions of wood, the appearance of new cambial zones close to the 

 separated segments of wood, which form also new bast, and finally also the 

 appearance of new strands of wood and bast in the pith itself, which are derived from 

 secondary meristem, and have an independent growth in thickness. The changes 

 start, in the branch investigated, from a swollen portion twining round a wire and 

 exposed to strong pressure, a fact which shows that they are at all events cdvanced 

 by mechanical causes. 



Fig. 23S. — Bauhiiiia spec. Transverse section of a stem, two-thirds the natural size, from Sclileicien's 

 Grundzujje. a all dotted figures are portion^ of wood, sometimes with remarkably large pitted vessels; 

 c bundles of wood, conspicuous by their whitish colour, with radial medullary rays, and arranged in a siuiple 

 circle (probablj; the original narrow medullary sheath, split up). With exception of the circle M the rest of 

 the wood consists for the most part of parenchyma, and the medullary rays take a sinuous course. '1 he 

 bands left white {b) between and around the woody bundles are masses of parenchyma and bast. 



It is doubdess similar anatomical changes which bring about the frequent splitting ■ 

 up of the xylem in the old stems of climbing Bauhmias^, especially of the .section 

 Caulotreius'^, of which the Fig. 238, which, according to Schleiden, is of a Bauhinia, 

 may give an approximate representation. In these Lianes however there is, in 

 addition to the phenomena in question, another also, which has not at all events 

 been shown with certainty to occur in other forms, viz. a long continued growth in 

 length of the old layers of wood, which may also be ascribed for the most part 



^ Compare Gandichaud, /. c. Tab. XVIII. Figs. 2, 3. 



^ [See V. Hohncl, Die Entstehiing der welligflachen Zweige von Caulotretus, Pringsh. Jabrb. Bd. 

 13. — Also, Warburg, in Botan. Zeitg. 1883, p. 617, &c.] 



