left, as shown by Kyrın (1923, p. 23), thus producing two rows of alternating 
segments (fig. 589). The central cell-row is only discernible in the upper end of 
the frond, later on it cannot be distinguished from the other longitudinal filaments 
filling up the central part of the frond. The outermost cell-layer has the function 
of assimilating tissue; it produces numerous long hyaline hairs (comp. K. ROSENVINGE 
1911, KyziN 1923), which arise in spring and early attain a considerable length, 
about 1 mm or more, with a diameter of about 10 w (fig. 590). They form a hyaline 
clothing on the fronds still growing. 
N N When the growih ceases, the hairs 
are shed and are therefore not met 
with in autumn and winter. 
The distinction between the assi- 
milating and the storage tissues is 
not very sharp. WILLE and HENCKEL 
(1902, p. 6) count up to 5 layers of 
the assimilating tissue while Kyrın 
(1923, p. 23) has only one. Within 
this follows a storage tissue which has 
also a mechanical function, and the 
central part of the frond is filled up 
by the conducting tissue built up by 
longitudinal filaments, primary and 
secondary, composed of long cells the 
transverse walls of which, as shown 
by WILLE (1885, p. 76, pl. VI, figs. 
74—76), are perforated by numerous 
fine threads of protoplasm. 
B The main stem is very distinct, 
Fig. 590. in particular in the lower part of 
Cystoclonium purpureum. A, upper end of frond showing the frond where it is less branched 
hyaline hairs. 200: 1. B, two superficial cells, the one bearing 
a young hair. 325:1. After living plants. than above. Near the base, however, 
a number of horizontal or downward 
bent branches arise which may reach a considerable thickness but only a length 
of a few, up to 5cm (fig. 591). In contact with the substratum they form low 
hapters which afford a better fastening for the plant (fig. 592). When with 
increasing age the surface of the plant is very much increased, the primary attach- 
ment disc would not suffice to resist the pull caused by the movements of the 
water. The basal shoots taper gradually towards the top but are not much branched. 
Upright shoots are sometimes given off from them, and they may thus have the 
character of stolons but new fronds are usually only produced near the primary 
ones, and the horizontal shoots have therefore no significance for the propaga- 
tion of the species. 
