Hxrriorr.— Morphological Notes on the New Zealand Giant Kelp. 551 
Habitat. 
Durvillea antarctica grows attached to rocks “ on exposed rocky coasts 
or steep cliffs, often in narrow crevices where the surf is very violent. 
During dead low water it hangs from the rocks, with the whip-like segments 
water the whole plant is violently tossed about in the breakers, and in 
stormy weather with tremendous force that would tear the strongest frond 
to pieces were it not split up into numerous laciniae, elliptical or circular 
in section " (Skottsberg, 1921, 
As Hooker noticed, Durvillea is generally associated with the pea large 
brown kelp, Macrocystis pyrifera. Durvillea grows close to and a 
to the rocks, forming huge banks of brown seaweed (Plate 54, figs. 1 pee 2), 
which are dashed about in the water = against the rocks by every breaker, 
while Macrocystis forms a second zone farther out, and its thin leaf- like 
segments can be seen floating on the Polos, rising and falling with each 
passing swell. The structures of these two seaweeds afford striking points 
of con cs The frond of Macrocystis is enormously developed, and exposes 
as great a surface as possible for assimilatory processes, while the stipe is 
very скин There is no strain on the stipe, its purpose being merely to 
connect the various portions of the frond and to act as a channel of con- 
duction, for which purpose it has developed its peculiar sieve-tubes. In 
Durvillea, on the other hand, ine stipe is of very considerable thickness, 
one having been measured of 12-5 cm. diameter. It grows out horizontally 
from the rock-face, and during low water has partially to support the huge 
segmented lamina which hangs from it; it must consequently be tough and 
leathery, and yet very pliable, to meet the great strain upon it. Portions 
. of the frond torn away from the plant may frequently be found, and some- 
times the stipe itself is broken across. The force of the waves may even 
tear away the holdfast with portions of the x uiii rock; and on looking 
down at a bed of Durvillea one may see ample evidence of the rough treat- 
ment to which it has been subjected. 
MORPHOLOGY AND ANATOMY. 
ee distinct regions can be r ecognized in the plant-body. Thes 
may be called (1) the holdfast (the “ radix " of Agardh and the “ haftscheibe ` ^ 
of Skottsberg), (2) the stipe or “ stem,” and (3) the lamina (Plate 55). 
(1.) The Holdfast. 
The holdfast е the plant to the rock. It is usually gie dae 
and circular in outline, forming one continuous disc. In one specim 
(fig. 1) collected on the New Brighton beach the tissue was lom apar "d 
leaving fissures in the structure similar to that described by Grabendorfer 
for D. Harveyi. The upper surface is light-yellow in colour, much lighter 
than the lamina and stipe, the lower surface, which grows towards the 
substratum, being dark і 
The holdfast grows stretched over the rock, adhering to it much after 
the manner of a leather sucker to a stone. The tissues grow round the 
jagged edges of rock and fit into the crevices, thus obtaining a firm hold. 
Holdfasts, of course, vary in size, according to the size of the plant 
attached, increasing in area as the plant і increases in size from year to year, 
The diameter is always several times that of the stipe attached, the smallest 
plant measured, in which the three regions of the plant were differentiated, 
