690 



KupFER : Anatomy and Physiology 



The bast-bundles lie so close to the circle of wood — a feature 

 according to Solereder characteristic of the Compositae — that no 

 cambium was distinguishable as such in any portion of the stem of 

 the growing plants. There are a number of thin- walled irregular 

 cells between wood and bast, most of which are sieve-tubes ; but 

 some must be of a meristematic nature, because the wood-cylin- 

 der gradually increases in diameter so as to be about 60 mm. at a 



Fig. 8. 



Cross -section of stem o^ Bai'i^iaris i^enis/i'iloides. 



distance of 15 cm. from the tip, 125 mm. at 19 cm., and i56 mm. 

 at the base of the plant examined. 



In an older stem taken from a herbarium specimen there were 

 present three definite wood-rings and a very clearly established 

 cambium layer. The wood on maceration was found to contain 

 spiral, pitted and annular vessels. Wood parenchyma is abundant, 

 but the medullary rays are obliterated. Around the primary bast- 

 masses when they occur, otherwise external to the sieve tissue, an 

 endoderm of one layer of rather large clear cells extends. Out- 

 side of this lies the cortex, of three or more rows of chlorophyl- 

 bearing cells. Outside of the bast-bundles, however, these cells 

 lose their chlorophyl and become collenchymatic. The angles of 

 the older stems from which the wings have been lost become heavily 

 suberized. 



