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1906] CHRYSLER—NODES OF GRASSES 7 
owing to increase in the xylem elements, which come to enclose the 
phloem more or less completely, as already described for Avena. 
A little further down they are joined on the flanks by several bundles 
from the internode above, each leaf-trace bundle with its tangle of 
contributing bundles forming a complex bunch of vascular tissue. 
A suberized endodermis surrounds the leaf-trace bundles in the node. 
The second rank of bundles of the leaf-trace also enter the central 
cylinder, where they are joined by other bundles, but soon return 
to the periphery of the central cylinder, where they give rise to some 
of the bundles which run through the next internode below on the 
border line between the sclerotic ring and the cortex. The smallest 
bundles of the leaf trace go no deeper than the sclerotic ring, and 
here fuse with other bundles found in this zone. Thus, the course 
of the bundles of different rank agrees with what STRASBURGER 
found in Zea. In the lowest part of the node, the very numerous 
bundles of the sclerotic ring anastomose and proceed downward, 
greatly reduced in numbers, while the bundles inside the central 
_cylinder also become much fewer, owing to completion of the fusion 
of the large leaf-trace bundles with cauline strands. 
The basal region of the stem has a cortex which differs from the 
aerial parts in being much broader and more spongy, on account 
of the large intercellular spaces. At any of the basal nodes the 
central cylinder is bounded by an endodermis, consisting of a single 
layer of rounded cells with suberized walls (fig. 6). Inside this is 
a narrow zone of vascular tissue, whose elements run circularly; 
then a wide zone, consisting of small bundles running vertically, 
and so closely packed together that it is generally impossible to dis- 
tinguish their limits. Bounding the two vascular rings on the inside 
is a band of sclerified cells which are in contact with the pith. As 
the photograph shows, leaf-trace bundles make their way into the 
central cylinder through wide gaps in this four-layered ring, and 
it may be clearly seen, even in unstained sections, that along the 
edges of such a gap the external suberized endodermis is continuous 
with the inner sclerified layer. All of the large leaf-trace bundles 
pass through such gaps, but the roots leave the central cylinder 
without causing a gap, as has been observed in plants of various 
groups. In the pith of the central cylinder are scattered many 
