Gymnogongrus plicatus Kützing, Spec. Algar. 1849, p. 789; Tab. phyc. 19, 1869, pl. 66; Harvey, Phyc. 
Brit. Vol. III, 1851, plate 288. 
Sterrocolax decipiens Schmitz, Actinoc. 1893, p. 397. 
The upright fronds spring from an expanded, thin firm disc intimately attached 
to the substratum, always stones, of a characteristic violet blue colour. By the 
colour it is usually easily distinguishable from other incrusting 
Floridez, as for instance Hildenbrandia prototypus, which has a 
similar consistence but is either blood-red or yellow. The crust may 
reach a considerable extension before the first upright frond 
arises. Young fronds 1—5 mm high are often met with singly on 
the sides of stones picked up in summer at 1 to 2 metres’ depth 
(fig. 542). But young fronds in greater number placed close together 
may also occur; then it is not always easy to decide whether 
they spring from one particular dise or from several fused together. 
Old specimens form light bushes composed of numerous fronds 
Fig. 542. 
Ahnfeltia plicata. Young 
frond springing from 
an expanded disc. 
10 : 1 (2). 
springing from an area of small extent. Such a case is shown in fig. 543 where 
Fig. 543. 
Ahnfeltia plicata. Cluster of fronds springing 
from a thin disc appearing light in the 
photograph, extending as far as to the dark 
area to the right. Slettings Grund, Store 
Belt. November. 3 : 1. 
The fronds are cylindrical, rigid, horny, branched by dichotomy 
and by lateral ramification. They are usually forked at the top 
about 100 fronds spring from an area with a maxi- 
mal diameter of 1 cm whereas the basal crust 
from which they have arisen has a maximal dia- 
meter of more than 2 In this case the crust 
has the appearance of being of single origin. 
The crust is built up of small almost squarish- 
cells, about 3 « in diameter, arranged in vertical 
rows, with firm, gelatinous cell-walls. The 
superficial cells are rounded outwards, but the 
outer cell-wall is scarcely thicker than the others 
(fig. 544). In older crusts this structure is some- 
times interrupted by tissue with larger, more ir- 
regular cells. 
The upright frond arises as a wart from 
the disc, a great number of the vertical filaments 
participating in it and showing 
divergence of the filaments, of 
which it is composed, and thus 
early showing conformity with 
the upper end of the cylindrical 
fronds. 
cm. 
not 
Fig. 544. 
Ahnfeltia plicata. Ver- 
tical section of crust 
625 : 1. 
and later produce lateral branches, which have usually the 
character of adventitious shoots, but the lateral branches may also arise near the 
top. They appear in great number on the older fronds when the apical growth has 
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