POSITION OF SCYTOTHAMNUS AUSTRALIS 139 
they become also more elongated, thus _ofiginating & “tight y 
depressed group of young hairs (figs. 4 and 5). Rapid transverse 
divisions now take place at the base of each hair, so that an inter- 
calary growing point is originated, which produces many more 
cells towards the outside than towards the inside ; and these outer 
cells elongate rapidly, so that the group of hairs projects far 
beyond the surface. At the same time the surrounding thallus 
has continued to grow, so we the ane group of hairs occupies 
a gr ed depression n (igs. 3 and 7). 
Pot iio were cut of many growing points 
both longitatiantiy ie and transversely, but in no case was a any defi- 
nite apical cell seen. The apex is occupied by a group of nee 
resembling neighbouring cells in appearance. In shape they are 
polygonal Beem and divisions take place in them parallel to em 
sides and base (figs. 8, 9 and 10). There is no r 
egular seque 
of divisions, aa the various tissues are not sharply differertiated 
in regard to their origin. Rapid divisions in the ngaavg cut off 
take place for some distance behind the growing point (fig. 11). 
Division ceases first in the inner tissue and the cells become 
gradually mature from inside pape 8 rae in the older parts of 
the pele only the limiting layer ristematic. 
the tip of the Cee is an blunt, and this 
Soscanes for the fact that the last section of a transverse series is 
always about a dozen cells in diameter. This is in strong con- 
trast with the form of the apex in Dictyosiphon feniculaceus, in 
which Murbeck (Vid. Selsk. Skrift. Math. Nat. Klass. Christiania, 
1900) saree a single apical cell 
The apices of branches vary in appearance according to the 
activity with which Paget is pro nse 
When s quite young its cells remain closely 
packed and divide wastioale over a — length; but as the 
form and structure, till finally, just before growth ceases, nei au 
small gro up of meristem, perhaps eight cells a ne nt tudinal 
section, is seen. The young cells are readily distinguishable from 
the bhiee ones by their contents. These in the young cells are 
dense and uniformly granular; when stained with Hoffmann’s 
Blue the chromatophores are indistinguishable, but the — are 
noticeable (fig. 11); in the mature cells numerous 
chromatophores are seen, embedded in a much less eae sa 
pag Ie while the nuclei are invisible or are only seen with 
great . 12). a 
iaeocpi —These are only found on plants in which gro “ 
has stopped. “These plants are distinguishable by a rather darker 
colour, and by a somewhat greater thickness of their ultimate 
branches, 
L2 
