210 MRS. WEBER VAN BOSSE ON PSEUDOCODIUM. 
distinguishing the Halimede from all the other Codiacem, are 
wanting. 
A section through the top of one of the branches of Pseudo- 
codium shows clearly that the growth of this plant is distinctly 
apical (Plate I. fig. 3). The same occurs in Halimeda. At the top 
the tubes are much thinner than lower down; they are densely 
filled with protoplasm, and give off many branches; each tube 
bearing its branches mostly on one side. These branches 
(fig. 4) may divide again or swell up at the apices, trans- 
forming themselves at once into vesicles, which on their first 
appearance are roundish and quite free, but soon grow oblong 
and acquire a generally hexagonal form in transverse section by 
mutual pressure. When they have assumed this form they 
adhere so closely together that a section or a piece of the frond 
must be exposed during a considerable time to the influence of 
caustic potash, or eventually be boiled in this solution, which 
dissolves the cork layer covering the surface of the vesicles, 
before they are detached from each other. Each vesicle is 
borne on a single shorter or longer stalk by which it is con- 
nected with the tube from which it sprang. These stalks may 
be very narrow at the base of the vesicles but a stopper of 
cellulose, so often seen in the tubes of the Codiex, was not 
observed (fig. 2). 
Besides the branches at the top, all due to apical growth, the 
primitive tubes may later on and lower down give off secondary 
tubes or branches, though more rarely. These secondary tubes 
or later branches grow in all directions between the other 
tubes. All the tubes are densely filled with grains of amylum, 
becoming intensely blue on applying cbloriodide of zinc. I was 
unable to study the chromatophores in living material while 
staying in Natal. 
In Codiwm the mode of growth is quite different from that 
of Pseudocodium. First of all the tubes that constitute the 
interior of the plant, are much thinner. Sections made 
through an apex of Codiwm tomentosum, indicate that every 
tube in this region swells at the top and transforms itself into 
one of the well-known clavate ramuli of the genus Codiwm. 
After this ramulus or vesicle has attained a certain size, a little 
protuberance appears at its base, and this grows out into a 
lateral tube (figs. 5, 6, 7, 8,9). The number of lateral tubes 
given off in this way may be one or more These new tubes 
