448 BOTANICAL GAZETTE [JUNE 
projecting inward to within one to four cells of the endodermis 
surrounding the bundles. 
The carinal canals are large, especially considering the youth 
of the specimen, and occupy about one-third of the bundle. The 
remains of one or two tracheids may adhere to the edges of the 
carinal canal, but all trace of the protoxylem has frequently dis- 
appeared over long stretches. The metaxylem forms two lateral, 
nearly parallel bands that converge slightly toward the periphery 
of the bundle. Usually each band consists of a single row of 
_tracheids, although locally there are often two tracheids lying 
side by side. In any case the band of metaxylem is markedly 
narrower toward the periphery of the bundle, because the tracheids 
here are always much smaller. The tracheids, of which each 
band contains from seven to fifteen, usually about twelve, increase 
steadily in size toward the interior of the bundle. This ‘‘inter- 
nodal” condition of the bundle, which in essentials is that char- 
acteristic of the whole genus, is shown diagrammatically in fig. 1, 
stage I. 
The node was slightly oblique, so that a section apparently 
nearly accurately transverse of the individual strands showed 
many different stages of nodal development. In the diagrammatic 
figures advantage has been taken of the opportunity to show two 
or three neighboring bundles in successive stages. 
__ The increase in the amount of metaxylem first becomes apparent 
about 1200-1600 uw below the level of the actual departure of a 
trace. The additional tracheids are situated between the inner 
ends of the bands of metaxylem. There is no regularity in ‘their 
order of development. Sometimes the first to lignify are those in 
contact with the tracheids of the lateral bands, but at other times the 
first additional tracheids to be formed lie in the middle of the 
parenchyma between the bands (fig. 1, stage 2). These tracheids 
are much smaller than the relatively large xylem elements situated 
near the inner ends of the lateral bands on which they abut. Gen- 
erally the crossbar which is thus formed is at first only one tracheid 
deep, but it may attain locally a depth of two or three tracheids, 
even before the bar is complete. Pari passu with its formation, 
other relatively large tracheids develop in contact with the inner 
