14 BOTANICAL GAZETTE [JANUARY 
On the other hand, the open sheath of the grass leaf may be con- 
sidered to be more primitive than the closed sheath of the sedges. 
Further, the cambium found in the grasses is here considered to be 
a primitive feature. But on the whole the Gramineae are to be 
_ regarded as a more highly specialized family than the Cyperaceae, 
though the families are evidently very closely related. 
Certain anatomical features of the grasses, such as the distribu- 
tion of the amphivasal bundles, seem to have an important bearing 
on the phylogenetic position of the family among monocotyledons, 
but since the anatomy of the group is as yet very imperfectly known, 
a discussion of this point would be premature. 
SUMMARY AND CONCLUSIONS. 
1. The grasses depart considerably from the scheme propcsed 
by von Mout for the course of the bundles, chiefly owing to the 
stem being hollow in most cases. The leaf-trace bundles are of at least © 4 j 
two ranks; of these the largest penetrate most deeply as they enter 
the central cylinder, generally receiving one or more bundles on 
each flank as they pass downward to the lower part of the node; 
the smaller leaf-trace bundles do not penetrate deeply into the central 
cylinder, but after anastomosing with other bundles pass downward 
either in the cortex or at the inner border of this. At the next node 
lower, these cortical bundles anast mcse with one another, and 
then with the bundles of the central cylinder which have come from 
fusions ‘with leaf-trace bundles at the next node above. 
2. The leaf-trace bundles, especially the larger ones, undergo 
a marked change as they enter the stem. This consists in the appear- 
ance of a distinct endodermis, and in an increase in the xylem, 
leading to the formation of a greatly swollen amphivasal bundle. 
Below the node these bundles resume the collateral type. 
3- Amphivasal bundles of the ordinary type, though absent in 
ihe ce internodes, are very commonly found in the nodes, and 
arise by fusion of collateral bundles which are generally leaf-trace — 
bundles. In some species they are more numerous in the nodes 
at the base of the plant, and where such nodes are crowded, the 
bundles may retain the amphivasal condition through successive 
internodes. The presence of amphivasal bundles in reproductive 
branches of plants in which these bundles are scarce in ordinary — 
