Herriott.— Morphological Notes on the New Zealand Giant Kelp. 557 
the lower portion of the lamina where no air-chambers are present 
thane: are only two kinds of tissue; the inner storage-tissue of the stipe 
disappears ig. 7, a section of this portion of ina, shows the 
arrangement of this e. The outer layers (b) are composed of cells 
arranged in more or less regular radial rows. In sections w been 
preserved in alcohol after picric acid these cells were flask-shaped, and the 
rows were distinctly separate. The cells were filled with darkly stained 
cell-contents. e inner cells of the layer lose their regular form, and 
show a tendency to elongate in various directions, and gradually » = 
into the second medullary layer (c), which is composed of a dens 
of filaments running parallel to the longitudinal axis of the plant. 
Sections of those segments of the frond which possess air-chambers 
show the same structure (fig. 8), but here the medullary tissue (c) is broken 
down in the centre of the very young portions of the segments, and the 
origin of the air-chambers can be seen (fig. 9). 
Growth takes place here as noticed by Grabendorfer (1885) in the outer- 
most layer of the lamina. These cells are richly filled with protoplasmic 
contents, and are in a state of active cell- division, both by tangential and 
radial walls. 
Air-chambers.—The air-chambers found in the frond of Durvillea ant- 
arctica are a distinctive mark of this species; they increase the widt 
the segments of the lamina, their gases distending it considerably. The 
each of which is Sarsouneded by a gni wall, ieasly istinguished on 
staining with methyl blue. In fresh specimens the walls are tough ‘ne 
elastic, but when dried they become papery. 
The gas contained in air-chambers of the Fucaceae was stated by early 
experimenters to be nitrogen. “ Wille added to der oxygen, and denied 
the presence of carbon dioxide " (Murray, 1895, p. 48). Some of the gas 
was collected at Taylor's Mistake and brought a to Christchurch, and 
analysed with Hempel’s apparatus. There was no CO, present. In BB c.c. 
of the gas after passing it through KOH there was no difference i in volume, 
remained, thus giving à volume of 12-4 c.c. of oxygen present. s gives 
a percentage ое оа of 22:54 oxygen and 77-45 nitrogen, showing the 
gas to be richer in oxygen than ordinary atmospheric air. There are no 
edge organs. fot absorbing the gases, which must therefore pass through 
-walls in solution in the water, and diey can do this only very 
oe 
CB кчы Warming states that the fucoids are able to absorb every trace 
of air present in the surrounding water, and, when that is all absorbed, to 
draw on the stores of oxygen contained in the air-chambers, and so carry 
on the process of respiration. This would account for the state of collapse 
which has been noticed in some of these air-chambers, as in the seaweed 
hich has px washed up in a shady place where little moisture can reach 
it. The can pass into the plant ied in solution in water, and when no 
water is present the plant is compelled to draw on its reserve stock. en 
the plant is exposed to the sun the heat expands the gas, and so keep s the 
chambers distended, while it also "а р the tissue of the plant, so that 
the process of assimilation cannot go o 
