1934 年 2 巻 5 号 p. 217-228
1. The filamentous fronds of the algae of the genus Aegagropila often form spherical tballi or hollow balls mostly due to rolling about on the bottom when they are at the mercy of waves and currents. The ball of each species and variety differs in shape and appearance in accordance with the nature of the filaments, viz., their height, type of branching, firmness, etc.
2. The ball of Aegagropila Sauteri from Lake Akan, Hokkaido, is rather compact in texture, composed of comparatively firm filaments radially arranged, and the cells at the peripheral layers of the ball are often worn off, being rubbed against the gravels on the bed of the lake. The cells of the underlying layers gradually grow until they come out from the surface to undergo the rubbing again. Where such trimming repeats effectively we find well-finished, velvety balls.
3. In A. Lagerheimii from Lake Toba, Prov. Tonnai, Saghalien, the ball is rather flexible, consisting of soft and delicate filaments, and consequently under a less effect of friction. Thus the ball doesnot assume a spherical shape, its surface being dishevelled with decumbent filaments.
4. In two small marshes near Lake Akan, i.e., Lake Toro and Lake Chimikeppu, where the rotatory movement of water near the shore is by no means active, we do not find A. Sauteri in its normal shape, but in the forms of irregular masses which are referable to forma profunda and var. Borgeana respectively. It is hoped that we can decide the relation between those va-rietal forms and the typical one by an experiment of transplantation.
5. The ball of A. Sauteri var. Borgeana from Lake Naiho, Etorofu Isl., Kuriles, is provided often with one or more pebbles in its hollow cavity. The wall of the ball consists of one to three layers of entangled filaments. Each layer is about 5mm in thickness, woolen cloth-like in texture.
6. Above mentioned pebbles in the hollow cavity of the ball are considered to beprimarily a part of substrata on the bottom of the lake on which this alga is found to attach forming compact cushions. A small part of this decumbent cushion sometimes becomes free from the substratum through the death of many of the basal cells, while smaller pebbles often do not detach from the under-surface of the free cushion and later on are enclosed by the latter.
7. Those cushion-like fronds detached from the substrata after having rolled near the shore first become hollow spindle in shape enclosing pebbles, if they attach, and then gradually become spherical by their further tumbling.
8. When the wall of a ball is composed of two or three distinct layers, they have no cellular connection between them and are separated without difficulty, though they closely contact with each other. The inner surface of each layer is occupied by dead cells which we take as the remains of the holdfasts of the primary frond of sedentary habit. The outer of surface the inner balls is vivid green in colour, as fresh as that of the outermost.
9. In other words, we have sometimes compound balls, so to speak, composed of two or three concentric balls of different origins. The primary or innermost ball has been enclosed by the secondary one transformed de noco from a free-floationg cushion newly detached from the substratum. As a result, there is no sign of cellular connection between these two hall; showing the growth of the outer ball from the filaments at the inner. In general, the compound balls are of large diameter, being more than 5cm.