614 Yendo. — On the Mucilage Glands of Undaria. 
gave me a favourable opportunity to observe the problematic structure on 
fresh specimens of Undaria pinnatifida , Sur., var. distans , Miy. et Okam. 
The material was fixed in picric acid as well as in sublimate solution, both 
saturated in filtered sea-water. It was brought back to the laboratory of 
the Agricultural College of Sapporo, and further examination has been 
carried on under various methods of treatment. I have arrived at the 
conclusion that the ‘ hyaline body ’ cannot be anything but a mucilage 
gland. As such a gland has never been known to occur in other members 
of the Laminariaceae, and as the species concerned are all confined to 
Japan, the results obtained in the present study, incomplete as they are, 
may not be unworthy of publication. 
The glands found in the species under consideration vary in their size 
and shape according to their stage of development and position in a pinnule. 
At an early stage they are ovate, with the sharper end towards the surface 
of the frond. They grow gradually into roundish, pyramidal or conical 
bodies, and may often elongate horizontally through the medullary tissue. 
Details of their development will be given afterwards. 
In the fresh specimens the substance contained in a mucilage gland is 
a colourless and highly refractive mass. In the material preserved in 
alcohol, after being fixed in the picric acid solution directly from the fresh 
specimens, the contents are also colourless. Okamura does not mention 
whether the specimens he studied had been preserved by any method of 
treatment, or were fresh ones. But in the dried specimens or in those 
preserved in formalin, or in those preserved in alcohol after being fixed in 
the sublimate solution, the contents are always brown as has been described 
by him. In the older parts which are nearly going to decay, in the formalin 
specimens, the contents become of a dark brownish colour approaching 
almost to black. As a ‘minute hole’ is situated just above each gland, a 
fresh frond in surface view shows numerous colourless spots, instead of the 
dark brownish dots, scattered in the brown epidermal layer. These spots 
are irregularly distributed all over the blade, but very few, if any, in the 
stem and rachis. I could not detect any in the rhizines and sporophylls. 
The number of glands in a blade varies considerably according to the 
part and to the age of the plant, as well as to the individual. In general, 
however, it may be safely remarked that they are proportionally most rich in 
the young pinnules of a frond at a post-embryonal stage, and that they are 
more numerous at the marginal regions than in the middle of a pinnule. 
When a plant has grown to its full size they occur in comparatively less 
numbers in the pinnules at the transitional region. The following table 
gives the manner of distribution. The figures show the number of glands 
in a square mm. : — 
