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 
2 | Vir A 
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Fic. 8. Cross-section of stem of Baccharis genistelloides. 
distance of 15 cm. from the tip, 125 mm. at 19 cm., and 166 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, 47 
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. 
