Phytogeny of the Cyperaceae. 1 1 
which is naked in Eleocharis , and provided with large leafy bracts in 
Cyperus . The great majority of the Cyperaceae, however, possess a 
jointed culm with a few or many rather long internodes. The lower 
node commonly bears only a reduced or sometimes even scale-like leaf, 
while the larger leaves occur higher up the stem. The leaf-base always 
forms a closed sheath for some distance above its node of attachment. 
The culm of Dulichium is cylindrical. The same is true of some 
species of Eleocharis in the young stages, but most of these are more 
or less flattened in the mature condition. E. mutata is unique in that 
its culm is sharply quadrangular with concave surfaces. With these 
few exceptions the culm of the Cyperaceae is triangular in cross-section ; 
sometimes more or less obscurely so, owing to the convexity of the 
surfaces, as in Scirpus lacustris , 5. Calif or nicus, S. caespitosus , &c. ; or 
with very sharp angles, as in S. robnstus , S. americanus , some Carices, &c. 
As previously stated, and as described by Pax (36), the aerial stem 
is commonly derived from the rhizome by a bifurcation of the growing 
point of the latter organ. In some cases numerous aerial stems arise 
from the root-stock by small lateral buds, as in Eriophorum alpinum. 
In still other cases the culm is terminal upon the short rhizome, as 
in short tuberous and annual species of Cyperus , Psilocarya , Stenophyllns , 
&c. At the point of origin of the aerial stem there is an extensive 
gap in the endodermal sheath of the rhizome, and through this gap 
the cortex and medulla are in free communication. The one unique 
exception to this rule is found in Scirpus fluviaiilis , which has been 
described on a previous page. The bundles of the first leaf-sheath are. 
derived from the superficial plexus of the central cylinder of the rhizome, 
while the cauline bundles are continuous with the deep-seated medullary 
strands. As these latter bundles begin to turn upward they branch 
more or less profusely, so that the number of bundles in the base of 
the culm is usually considerably greater than the number of rhizome 
strands to which they are directly traceable. Moreover, it is to be 
noted that these bundles of the culm-base are always collateral, whatever 
the nature of the rhizome strands from which they are derived. 
The apical development of the culm has been studied by Miss 
Anderssohn (1), Guillaud (19), and Van Tieghem (56). It presents no 
features of special interest in the present investigation beyond the fact 
that here, as in some other Monocotyledons, cambial activity continues 
for some time after complete differentiation of the fibro-vascular bundles. 
We shall have occasion to refer to this fact again presently. 
Dulichium is the only hollow-stemmed form among the Cyperaceae. 
Eleocharis , a few aquatic species of Scirpus , and Cyperus Papyrus possess 
very large medullary air-spaces, separated by delicate plates of parenchyma ; 
and many other species present this feature in a much less conspicuous 
