18 
K. MI V AUK 
upper surface 1 '“ 0 of the blade but usually not on the median fascia 
nor on the under surface, 195 developing from the lower portion 
upwards as a continuous patch, becoming discontinuous and scat- 
tered in the upper portion. In the specimens collected at Moyoro 
Village, Biroo district, Tokachi Province, and in the vicinity of 
Cape Erimo, Hidaka Province, the sporangial sori were found not 
only on the marginal portions of the upper surface but also on 
the median fascia of the under surface. The sori begin to develop 
from the middle of July and come to maturity in August and Sep- 
tember. In the period between the early autumn and the beginning 
of the winter, old fronds are detached from the substratum and 
new ones begin their growth. Owing to the damage caused by 
drifting ice or to other reasons, new plants sometimes happen to 
appear first in the following spring. Such plants, commonly called 
“Mizu-kombu”, are of very narrow blade. They produce sporangial 
sori towards the end of October or at the beginning of November. 
K.jeij.man described the present species as having no mucilage 
duct in either stipe or blade. In the abundant specimens at hand 
from Hidaka and Iburi Provinces, however, the author could rarely 
find an individual bearing a row of mucilage ducts in the stipe. 
On the other hand, the stipe of the specimens collected at Shira- 
nuka, Esan, and Biroo was found to be entirely destitute of 
mucilage ducts. Thus variable was the existence of the ducts in 
the stipe, while their presence in the blade was ascertained to 
be constant. The present species differs from others in the fact 
that the arrangement of the ducts is quite irregular. The ducts 
would be entirely lacking under both surfaces in a part of a blade, 
while in other parts of the same blade they would be present in 
the tissue under one surface but absent from the tissue under 
the other. This species is characterized by having mucilage ducts 
not in the form of an extensive continuous net-work but in the 
form of small broken fragments of a net-work. (Plate 29, Fig. 5). 
The medulla of the blade is composed of filamentous cells running 
in every direction, just the same as that of the stipe, and when 
immersed in fresh water it swells up remarkably to occupy 1/3 
of the thickness of the blade in cross section. (Plate 29, Fig. 2). 
Habitat. Growing on rocks between the low-tide-mark and the 
18) 19) Cf. Foot-note no. 6 on page 5. 
