463 
In most of the Danish species, however, I have observed that in specimens gathered 
in spring or in great depths these bodies were true chromatophores giving to the 
trichoblasts a light rose colour. This phenomenon is particularly conspieuous in 
Polysiphonia elongata f. baltica which just occurs in deep water. In Rhodomela the 
chromatophores of the trichoblasts are distinctly rose-coloured, but they are finally 
decoloured in the adult trichoblasts which are shed at the beginning of the summer. 
In Brongniartella byssoides they are persistent and remain coloured during the life 
of the plant. 
In Polysiphonia nigrescens the cell-sap of the trichoblasts may be rose-coloured 
in April, later brownish. 
The ramification of the primary axis of the trichoblasts is regularly alternate, 
biseriate. The first branchlet is always given off on the anodie side (to the right 
when the spiral turns to the left), from the second joint, in Rhodomela often from 
the third. In the female trichoblasts the first branch is given off from the fourth joint 
and most frequently on the anodic side. In female trichoblasts of Pol. Brodiæi two 
branches were found on the same joint, one above the other (p. 381). 
2. Unicellular hyaline hairs do not occur in the Rhodomelaceæ. Only in Brong- 
niartella byssoides such organs may sometimes be met with in peculiar pointed shoots 
without trichoblasts (comp. p. 406); but they might perhaps better be interpreted as 
a sort of rhizoids. 
3. The branches arise in different manners. 
a) In Polysiphonia urceolata, P. elongata, P. nigrescens and Rhodomela they 
are produced directly from the youngest segment under the apical cell, usually in 
the place of a trichoblast in the spiral. In some species, at any rate, the branch- 
producing segments are higher than those which give rise to the trichoblasts or do 
not produce any sort of lateral organs (P. urceolata, fig. 344, P. elongata). To this 
group belongs Odonthalia, which is destitute of trichoblasts, and Heterosiphonia which 
has a sympodial growth. 
b) In the other species of Polysiphonia, in Brongniartella byssoides, Chondria 
dasyphylla and Laurencia pinnatifida the normal branches arise as axillary buds 
of the trichoblasts. In Brongniartella they arise rather late when the trichoblast has 
reached a pluricellular stage. In Polysiphonia they arise much earlier, simultaneously 
with the trichoblast or nearly so, and it seems that the branch-producing trichoblasts 
are, at their first appearance, bigger than the sterile ones (comp. K. R. 1884 p. 29, 
rés. p. 5, figs. 34—40). The branches in Polysiphonia are thus not branches of the 
trichoblasts as OLTMANNS thinks (Morph. u. Biol. d. Alg. 1904 p. 609). The basal cell 
common to the trichoblast and the branch belongs as to its lowermost part to the 
stem. The first joint of the branch, common with the trichoblast, cuts off peri- 
central cells on its outer surface, but the central cell of this joint keeps the proto- 
plasma continuity with the trichoblast through a longitudinal wall between the peri- 
central cells or the segmental wall between the first and the second joint (figs. 379, 
388, comp. K. R. 1903, p. 468). 
