8 BOTANICAL GAZETTE [JANUARY 
bundles, nearly all of which are amphivasal, and where the nodes 
are crowded, as they are at the very base of the stem, the amphivasal 
condition is retained by bundles from one node to another, though 
in the more elongated internodes, found a little higher in the stem, 
only collateral bundles occur. The contrast between the upper 
and the basal nodes is indeed striking, for the former show no amphi- 
vasal bundles running longitudinally in the pith, except the enlarged 
leaf-traces. This feature of the aerial node may be partly accounted 
for by the thinness of the diaphragm in which run the anastomosing 
bundles, which are generally amphivasal. 
AMPHIVASAL BUNDLES 
_ Although these have been repeatedly reported as occurring in 
the subterranean stems of monocotyledons (see STRASBURGER, 4, 
p. 348, footnote; DEBARY, 2; SCHULZE, 5)3, the only references to 
their occurrence in grasses that have been found are by STRASBURGER 
(4) and Jerrrey (9). Duvat-Jouve (1) figures the rhizomes of 
many grasses, but shows no amphivasal bundles. Yet an cxamina- 
tion of the nodes of some of the same species shows that the bundles 
in question occur here. Two sorts must be distinguished in this 
family: (1) the swollen portion of a leaf-trace bundle, the xylem 
consisting largely of a mass of tracheids running irregularly; (2) the 
type usually figured, the xylem forming simply a ring of vessels. 
The features of the first class have been described under Avena. 
Such a bundle is always enclosed by an endodermis which generally 
has pitted or reticulated walls, and shows, in addition to the ordinary 
metaxylem elements, a large number of reticulated tracheids, which 
almost or quite enclose the phloem. All the species examined show 
these bundles, from hydrophytes such as Zizania to xerophytes such as 
Ammophila, and there appears to be no relation between the size 
which a bundle attains at its widest part and the condition under 
which the species grows. If, as already suggested, these bundles 
serve to store up water, it might be expected that they would be 
poorly developed in aquatics, but the only peculiarity of the bundles 
found in such plants is the slight lignification of the xylem, a char- 
3Since the above was written, Horm has reported the occurrence of amphivasal 
bundles in the rhizome and also the aerial stem of Croomia pauciflora (Amer. Jour. 
Sci. 20:50-54. 19¢5). 
Be ee 
