353 
All the cells contain one nucleus and numerous small disc- 
shaped chromatophores. The colour is brownish-red. By treating old 
parts of the plant with concentrated sulphuric acid the cell-walls 
were stained blue, which must be due to the presence of iodine 
in the plant. 
The upper pinnule not rarely end in a hyaline hair, as 
first mentioned by PrincsHEem (1861 PI. VIII fig. 2) and later 
by myself (1911 p. 210). As shown by me, the young hairs con- 
tain a number of feebly coloured chromatophores, but these are 
later reduced, and in the full-grown hairs they are only visible 
as very small colourless grains (fig. 284). These hairs often 
cause sympodial ramification, the cell on which the hair is 
borne growing out about in the direction of the branch and push- 
ing aside the hair. Such hairs were found frequently but not 
always in the specimens collected in April to September; in April 
and partly in May the hairs were short, but in autumn and win- 
ter (October, November, January) no hairs were met with. 
The pinnulæ were sometimes found growing out into arti- 
culated, long-celled filaments the cells of which when lengthening 
take a feebler colour. They might perhaps be considered as ab- 
normally de- 
veloped rhi- 
zoids. As they 
are hair-like 
but different 
from the nor- 
mal unicellu- 
lar hairs they 
might benam- 
ed  trichoids. 
They were 
most strongly 
developed in 
a loose spe- 
Fig. 285. 
Plumaria elegans. A, form with divaricate pinnulæ. B, pinnulæ trans- Alex © 
formed into rhizoid-like filaments. 4 150:1. B 80:1. the cortex early covering the pri- 
Fig. 284. 
Plumaria elegans. 
Hairs with numerous 
small reduced chro- 
matophores and de- 
formed nuclei. 240 :1. 
cimen found in the Baltic where 
it must have been introduced by 
the currents. The same specimen 
was remarkable by its divaricate, 
acuminate pinnules (Fig. 285). 
As shown by NäÄGeLı (1847, 
p. 207, see also CRAMER 1864), 
