523 
there is then only a feeble or no narrowing at the boundary between the old and 
the new frond (fig. 498 b, c); but when the segments are pointed at the end of the 
season, the growing zone is very short; the new segments are connected with 
the old ones by a narrow stalk (fig. 498 a). In both cases the periodicity of the 
growth is connected with a periodicity of the breadth of the frond, the latter be- 
coming greatest in the middle of the growing period. The apical growth and dicho- 
tomy of the frond is usually not continued during more than two or three years. 
The growth then ceases and 
the upper portion of the flat 
frond is very often disorganised. fi 
This mode of growth occurs 
in particular in broad speci- 
mens reminding one of the arc- 
tic f. interrupta (fig. 488 b). In 
some cases new leaves arise 
as adventitious shoots from 
the cicatrized upper border 
of a flat frond (fig. 498 b, 
above in the middle, comp. 
Harvey Phyc. Brit. pl. 20, 
fig. 3). 
Besides the apical growth 
and dichotomy, a branching 
by adventitious shoots or proli- 
ferations arising at a lower 
level are very characteristic 
of the species. The prolifera- 
tions become long shoots terete 
below, upwards gradually flat- 
Fig. 498. 
lened and more or less divided Phyllophora Brodiei, fronds branched by dichotomy. a from Lille Belt, 
1 . ] March. b, Fæno Sund, April. c, from UK, Langelands Belt, May. d, Store 
‘4 7 EJ 
by og they arise from Belt, November. e, Busserev at Frederikshavn, December. a, b,e ?/, nat. 
the margin or, not rarely, from size; c 2:1. d */, nat. size. 
the flat side of the frond 
(figs. 499, 502). Their number is less than in Phyll. membranifolia, sometimes only 
one, and they may be entirely wanting. When the branching by proliferations is 
much pronounced, the apical ramification is often feeble; the growth of the upper 
border ceases at an early period. The growth of the single proliferations sometimes 
endures only one year; the growth is then taken up again by the new prolifera- 
tions that may cease to grow in the next year, and so on, and a series of genera- 
tions of proliferations may thus be produced. This takes place particularly in 
specimens growing in the inner waters in deep localities where the water is agitated 
by the current but not by the waves. In the specimen pictured in fig. 499 at least 
67% 
