105 
the trichoblasts; they are developed in trichoblasts of various position, and the 
cystocarps are therefore placed on the edges and on the flat sides of the frond as 
well. The development of the procarps and the cystocarps has been 
carefully studied by Kyrın (1923, pp. 125—129). In the ripe cystocarp 
the wall consists only of three or four cell-layers, the innermost ones 
being disorganised and transformed into a tough mucilage (FALKENBERG 
p. 246, pl. 23 figs. 20—21, KyziN p. 128 fig. 80 d). 
The tetrasporangia are immersed in the cortical layer of the upper 
ends of the frond; according to Kyrın (1923 p. 130) they arise from 
young cortical cells by divisions similar to those by which the spor- 
angia arise in the pericentral cells of Polysiphonia. 
The germination of the tetraspores has been examined by Kyrın 
Fig. 339. 
Laurencia pin- 
(1917) who showed that a pluricellular basal disc is early developed. AO Moe: 
The young disc is composed of connate radiating filaments, it increases tion of frond 
gathered in 
in diameter by marginal growth and early begins to produce new erect ale ie 
shoots by budding from the surface. The new shoots resemble the branches have 
. recommenced 
primary one (fig. 338 A). rn DL. 
The species has been met with in all the seasons. It occurs at 
low-water mark or a little deeper, down to 6,5 meters’ depth. It grows most frequently 
on Fucus vesiculosus and F. serratus, further on stones and more rarely on Chorda 
Filum a. 0. alge (Chondrus crispus, Furcellaria, Cystoclonium, and 
the blade of Laminaria digitata). It usually attains a length of 
2 to 5 cm, more rarely up to 7 cm. The fructification takes place 
in summer. Antheridia have been met with in May and June, 
cystocarps in May to September, in the last month partly empty, 
and tetrasporangia in May (unripe) to August. 
According to GREVILLE and Harvey, the species is annual, 
and it may certainly frequently be so also at the Danish coasts. 
Young plants are to be found in summer and autumn, July to 
September (fig. 338 A); they produce a number of erect shoots 
Fig. 340. which remain sterile in autumn and winter and at the end of 
Laurencia pinnatifida. the winter attain a length of 3—5 cm. In winter the growth ceases 
ee, que but it recommences at the end of the winter. In March and 
reached its full size; me April the new-formed tips of the frond are easily recognised and 
old frond is darker, cov- sharply limited against the old frond, but only about 1 mm long 
ered with epiphytes. = : n 
13:1. (fig. 339). In summer the new shoots have reached their full 
size and are distinguished from the old frond by the colour and 
by the want of epiphytes (fig. 340). The fertile erect fronds probably die in autumn, 
but the basal disc seems to be able to continue the development, growing al the 
margin and producing new erect fronds fructifying next year. Thus, the basal dise 
shown in fig. 338 B, collected in June, is probably more than one year old. 
The species occurs in the Danish waters with rather high salinity but requires 
D. K. D. Vidensk. Selsk. Skr., 7. Række, naturvidensk, og mathem. Afd., VII, 3. . 52 
