Although much attention has been given to the nutritive value of the seaweeds，we find
few reports on the relation of the tissue and its microingredients. Up to date the authors reported on the light and electron microscopic observations on the tissue of Undaria pinnatifida，the distribution of its microingredients and a fading of the pignient. This time some observations on the mucilage gland，which is under the outermost layer and whose finestructure has not yet been studied， were carried out.
The fresh materials were obtained in the sea along the cost of Onomich in Hiroshima.
One of them was non-treated，another was frozen，a third paraffin embedded and the last two were Epon embedded after double fixation of 2% glutaraldehyde and 1% osmic acid and dehydration. For the light microscopic observations Epon embedded materials were serially sectioned in 5 um thick and stained by toluidine blue. For the electron microscopic observation both Milloning staining and uranyl acetate were used. The contents of the mucilage gland are clear and it is difficult to observe its finestructure without staining. The followings are the results obtained from the above staining methods.
1) The contents of the mucilage gland consist of glucoprotein and the lipid is not observed.
2) The density of the sticky contents and the membrane structure are easily observed by the toluidine blue staining.
3) Electron microscopic observation reveals the di妊erent stages of the development and
the finestructure of the sticky contents in the micilage gland.