196 Gibbs . — Bio-histological notes on some new 
Areschoug 1 describes transpiratory parenchyma as distinguished by large 
lacunae, and where rapid transpiration is necessary the palisade tissue is 
reduced and the mesophyll increased. When transpiration is reduced, a 
system of water storage or palisade is elaborated. In Fuirena sub-digitata 
this result is obtained, and the air canals are replaced, through the whole 
length of the leaf, by water-storage tissue associated with stomata that are 
not only sunk but have their apertures partially covered over. 
Vascular tissue. The vascular bundles are collateral. The phloem, 
directed towards the dorsal surface, is composed of small thin-walled cells 
with well-marked companion cells. A certain amount of starch is present 
in the phloem. The two vessels are always accompanied by a protoxylem 
lacuna and lignified parenchyma (PI. XII, Fig. 1 2 ,px. 1 . and Ip.). 
Bundle-sheaths. A sheath of large thin-walled parenchymatous cells, 
colourless in contents, surrounds each bundle (Fig. 12, w.s.), the water-sheath 
noted by Rickli 2 as occurring in many Cyperaceae. The inner f Paren- 
chymscheide’ which the same author figures as characteristic of the 
Chlorocyperaceae, including Fuirena , was not observed in the species exa- 
mined, though in Fuirena stricta a very well-marked sclerotic sheath of 
single cells surrounds each bundle inside the water-sheath. No starch was 
traceable in the cells of the latter, towards which the palisade cells show a 
marked convergence. The connexion with the epidermal water-cells pro- 
vides an organization which surrounds all the vital parts of the leaf, not only 
reducing the temperature, but ensuring turgescence by eliminating tran- 
spiration on the most exposed surface. Thus protection against transpira- 
tion is effected by a very simple and, as we have seen, plastic organization, 
while other plants have to meet the difficulty by elaborate contrivances, 
involving much greater specialisation of structure, such as extreme cuticu- 
larization or collenchymatous thickening of the epidermal walls, secretion 
of mucilage, or hairy coverings. 
The anatomical characters of the three Fuirenas examined are thus seen to 
be considerably modified by their environment, though from a general point of 
view their organization is on the well-marked developmental lines common 
to all the genera of the order. In Fuirena Oedipus the plant provides for a 
short and rapid growth-period bylaying down starch reserves in the basal node 
of the stem. This is an advance in organization to storage in the rhizome, as it 
not only ensures the supply being further removed from the constantly wet 
substratum in which roots and rhizome lie, but also provides a short cut 
when the plant starts into growth, as the starch has not to be transferred 
from the rhizome to the aerial tissues. In the structure of the leaves, the 
hygrophilous habit is shown in the breadth and length of the lamina, also 
1 Areschoug, Der Einfluss des Klimas auf die Organisation der Pflanzen, insbesondere auf die 
anatomische Struktur der Blattorgane (Engler’s Bot. Jahrb., n, 1882, pp. 511-526). 
a Rickli, 1 . c. 
