• Neomeris dumetosa , L amour. 
589 
normal structure. A section of the growing-point at this 
period (Fig. 18) shows the origin of this new type of appendage 
to be due to a precocity of development of the first dichotomy 
of the member, accompanied by a laying down of septa above, 
instead of below, the first point of bifurcation ; all earlier 
stages, therefore, cease to be recapitulated, the third node 
from the apex is already unmistakably Stage IV, and the 
growing-point henceforth lays down only appendages of this 
new and improved pattern. In the nearest approach to the 
actual transition obtainable in the neighbourhood of the apex 
(Fig. 18), the junction of the secondary segments to form 
a continuous cortical layer was just completed in the 9th 
node behind the apex. The number of members in a single 
whorl now reaches 16-22,, and this number steadily increases 
with increasing bulk of the plant. 
Stage IV may be regarded as the adult sterile condition ; 
its formation may be continued over 200-300 nodes, the main 
axis slowly increasing in length to 25-3 o mm. Compensating 
contraction of the older internodes still proceeds, and, in an 
older plant of this stage, the two-scarred basal segments may 
be traced almost to the base of the plant. Before being 
entirely obliterated, the whorls of old scars become pulled 
down so close together that it often becomes difficult to 
isolate the scars of one particular node ; at the same time, 
the individual scars become greatly elongated transversely 
to eye-like markings, while the cellulose plug which closes 
the septum retains its sharp contour to the last (Fig. 20). 
Reversion to a previous type of appendage on a large scale 
occasionally happens, but only in one case was a considerable 
interpolation of Stage II observed. Such phenomena may 
possibly be the result of injury to the growing-point, and in 
these cases the thallus will appear markedly constricted. 
Similar non-calcified constrictions have been described by 
Cramer in N. Kelleri , and these again present suggestions of 
the normal structure of Cympolia. 
Calcification of the lateral appendages sets in after forma- 
tion of a number of whorls of Stage IV, which may reach 
