Rhodesian species of Fuirena t Hesperantha y and Justicia. 19 1 
regularly on the periphery, each accompanied by a hypodermal strand 
of fibres alternating with large lysigenous air-spaces (Fig. 11). Tannin 
sacs are present, and starch is massed in the two or three layers of 
parenchyma (Fig. 11, t.s. st.) which occur between the phloem and the 
hypodermal strands of fibres accompanying the cortical bundles. No starch 
was found in the sheath of colourless cells which surrounds each bundle. In 
this section the epidermis is without stomata, is thinly circularized, and 
its cells are smaller over the hypodermal ribs. 
Basal internode . As has been already described, the lowest internode 
of the aerial stem is curiously modified for starch-storage purposes, and its 
form is due to a proliferation of the cortical tissue of the internode. The cross 
section is circular (PL XII, Pig. 9), the lysigenous air-spaces of the aerial 
stem being quite suppressed, though the sclerenchymatous ribs are still 
present, and the cells of the epidermis are smaller where they pass over 
them. The cortical bundles are pushed more towards the centre, showing 
that it is the starch-containing layers of parenchyma already indicated 
in the aerial stem (PI. XII, Pig. 11, si.) which are responsible for the re- 
serve storage tissue of the pseudo-bulb formation. Small schizogenous air- 
spaces occur freely in the cortex, and increase in size towards the medulla 
(Fig. 9), which is identical in structure with that of the unmodified por- 
tion of the stem (Fig. 11). All the cells, including those of the thin 
medullary plates of parenchyma, are densely packed with starch, result- 
ing in a structure of corm-like consistency, the rigidity of which is due 
entirely to its stores of reserve material ; the mechanical thickening, notwith- 
standing the great increase of surface, being no greater than in the upper 
portion of the stem. Tannin sacs are very numerous in the cortical region. 
In longitudinal section (PL XII, Fig. 10) the subtending leaf-trace 
bundles are seen to insert themselves on the cortical bundles of the stem 
at each node (Fig. 10, l.t.b.) essentially as figured by Plowman 1 for 
Dulichium arundinaceutn Brit., and the arrangement is similar in the 
basal node, in which the reserve food tissue is strictly limited to the 
proliferation of the cortical parenchyma. 
Examples of special organogenic modifications for the storage of 
reserve food material are of exceptional occurrence in the Cyperaceae, and, 
as far as investigation goes up to the present, are entirely limited to the 
rhizome. Holme 2 has recorded for Fuirena squarrosa Michx. a tuberous 
development of one of the internodes of the rhizome, which takes the form 
of a shoot with the growing point arrested, the tissue composing it being 
packed with starch. He cites this case as being very rare in the genus, 
comparing it with the tuberous rhizome of Cyperus esculentus Linn, and 
C. Rhymatodes Muhl. described by Duval-Jouve 3 as being formed from 
1 Plowman, 1 . c. 
2 Holme, Studies in the Cyperaceae (Am .Journ. Sci., 1897, pp. 13-25, Pis. 1-2). 3 . Duval-Jouve, l.c. 
