357 
fig. 290 the central axes of the pinnulæ traverse the cortex of the stem and are con- 
nected with the central axis of the latter through large pits. The greater part of the 
cortex consists of large rounded cells 
which have principally the character 
of storage cells; they contain numerous 
starch grains and narrow, branched 
chromatophores. The outermost cells 
are small and constitute a one- or two- 
layered assimilatory tissue. The cells of 
the central axes going out to the pin- 
nulæ are also rich in starch, but the 
central axes of the stems do not con- 
tain starch; the granular plasma of their 
cells is concentrated in the upper half 
of the cell while the lower half has 
only a thin layer surrounding the va- 
cuole. In the somewhat older stems a 
number of thin rhizines arise from the 
inner corti- 
cal cells, for- 
ming a layer 
surrounding 
the central Fig. 290. 
axis and in- Ptilota plumosa. Longitudinal section of frond in the plane 
1 fs of ramification. 110: 1. 
creasing in 
thickness. This production of rhizines later advances out- 
wards, so. that the cortical cells in older shoots are partly 
separated by thick bundles of rhizines, and transverse 
sections of old stems may in great part be composed of 
rhizines. All the cells contain one nucleus. 
Hyaline hairs have not been met with except those 
which occur near the procarps and which will be men- 
tioned below. 
The tetrasporangia are terminal on short monosipho- 
nous filaments borne on the margins of the pinnule and 
terminal on the pinnæ; they are tetrahedrically divided 
(fig. 291, comp. Kyrın 1923 p. 59, fig. 39). 
The antheridia have been shortly mentioned by Pnır- 
Fig. 291. 
Ptilota plumosa. Pinna with tetra- 5 4 | 
sporangia. 230 :1. Lips (1897, p. 365) who says that they “cover the tips of 
the branches, and correspond closely in appearance to 
the similar structures in Plumaria, which have been figured by BurrHam (90)”. I 
have found antheridia in a dried specimen dredged in the Kattegat in May. They were 
D. K. D. Vidensk. Selsk. Skr., 7. Række, naturvidensk. og mathem. Afd. VII. 3. 46 
