364 
specimens from the Kattegat. Such specimens form a transition to others which have 
normally 3 or 4 ranks of pinnæ, as most of the specimens found in the Skagerak. 
3 ranks were most frequently met with. When the number of pinnæ in the whorls is 
constant, they are usually superposed, though not regularly. In these specimens the 
long shoots are not contained in one plane but issue in different directions. Accord- 
ing to BERTHOLD (1882 p. 614), the ramification is dependent on the light, so that 
plants growing in unilateral light branch in one plane, while plants illuminated 
equally from all sides bear branches 
on all sides. This, however, cannot 
be the sole determining factor, for in 
all the specimens examined by me from 
eight localities in the North Sea and 
the Skagerak the pinnæ were arranged 
in 3 or 4 rows, while the specimens 
from all the localities within Skagen 
were branched in one plane and at 
most bore unbranched pinnulæ on the 
face of the frond at the angle of the 
branches, or rarely on a few adjacent 
joints too. Only in specimens from 
the south side of Skagens Gren and 
in one specimen from Groves Flak 
(Ke, 26 m) the pinnæ were arranged 
in 3 or 4 rows. These specimens were 
all growing in water of comparatively 
high salinity. In the latter specimen 
the pinnæ were arranged in 4 rows, 
those on the flat side were, however, 
Fig. 300. feebler than the others, and in many 
Antithamnion Plumula. Tetraspore-bearing shoot with un- 5 2 
usually numerous gland cells, from Lille Belt. August. Re- CASSER Pınn® occurred on the flat side. 
duced pinnæ. 380: 1. The pinnæ only bear pinnulæ on 
the upper side, and these may be un- 
branched or they bear pinnulæ of the second order on their upper side. More rarely 
the pinnæ are unbranched or very little branched, as in some specimens from Herthas 
Flak in more than 20 meters depth (fig. 299 B), which, however, bore typical branched 
pinnæ in the lower part of the plants. The pinne are at first directed upwards, later 
usually divaricate, or some of them may even be recurved. Only in specimens from 
Skagerak off Lonstrup (8 m) a great number of the pinne were recurved. The pinnæ 
and pinnulæ are finally pointed, the ultimate cell ending in a thin point consisting 
only of the cell-wall. This pointing takes place at the end of the period of growth; 
in the later part of July and in August acuminate pinnæ may occur, even near the 
growing point, while in the first part of July specimens without acuminate pinnæ 
may be met with. 
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