84 CROCION ACHILYDOPHYLLUM 
the hadrome vessels have a brick-like arrangement, the entire 
strand of continuous. circumference enclosed the central pith. 
The tracheae though differing in lumen are mostly all of the reti- 
culately pitted type, at times, however, spiral and annular vessels 
are found. In the rootstock the reticulately pitted vessels are much 
shorter in length than in roots, with cross wall markings as plainly 
evident as in the latter. The medula is composed of rather thin- 
walled cells very rich in starchy deposits. Calcium oxalate crystals 
are quite abundant in both the intra- and extrastelar funda- 
mental tissues. 
‘ 
THE Stem. (Fig. 17-18). 
The mestome bundles are open collateral with hadrome 
endarch tetrarch. he cambium is confined to the bundles between 
the leptome on the outside and the hadrome on the inside (intra- 
fascicular cambium) being interrupted by the seeming equality 
of the intrastelar fundamental tissue, in which case the interfasci- 
cular cambium (between the bundles) is hardly at all developed 
constituting, more or less, an interrupted cambium ring. ‘The 
bundles are more or less circular in cross section. The ducts of the 
protohadrome are of small diameter mostly annular, and pass grad- 
ually to those of the metahadrome and secondary hadrome with large 
caliber and spiral in type. The scalariform pitted ducts are only 
occasionally found. ‘The cells of the hadrome parenchyma are thin- 
walled and elongated along the vertical axis of the stem (Fig. 18 W). 
The leptome tubes are approximately 1o times longer than broad, 
of thin walls, and are associated with the companion cells with 
similar walls attaining but half the length of the cells. The 
cells of the medulla increase both in width and length as they reach 
the centre of the cylinder remaining thin-walled throughout their 
existence. Crystals of calcium oxalate are found within the pith. 
‘The endodermis composed of cells of about the same length as 
breadth with starch grains limits the stele dipping somewhat toward 
the medulla between the fibrovascular strands. The cells of the 
cortical region are all parenchymatous and no sclerenchyma was‘ 
found. Chlorophyll is confined mostly to the outer cells of the 
cortex, and small intercellular spaces are present throughout this 
region. ‘The epidermal and the underlying hypodermal cells, 
including possibly the cells of the third layer, are much alike as 
to size, shape and arrangement. 
