Organic pollution of the Ina River and it's branches, the Minoh River and the Yono River, was estimated numerically by using the diatom assemblage index (DAIpo). And the water quality charts of each river were made using DAIpo. Results were the following. (1) The Ina River: DAIpo values decreased gradually toward the dow n stream. The DAIpo value of the point of water source for Ikeda City was ca.60 (α-oligosaprob) and for Toyonaka City was ca.55 (α-oligosaprob). River pollution index (RPID), whose value is able to be shown the general degree of pollution of river system, was 63. (2) The Minoh River: DAIpo values of two sampling sites in the upstream were very high but decreased rapidly toward the downstream. The DAIpo value of the point of water source for Minoh City was ca.70 (β-oligosaprob), and the RPID was 67. (3) The Yono River: DAIpo values were lower in the up s tream rather than in the downstream. The DAIpo value of the point of water source for Ikeda City was 59 (α-aoligosaprob), and the RPID was 56.
Three kinds of biotic indices, viz, diversity index, Beck's index (BI) and Pantle and Buck's saprobity index (SI), were compared and the ability of each index for indicating the phases of water pollution was discussed. Field surveys were conducted at the Asa Kawa River in Tokyo, Japan. Though the diversity indices have so far been used commonly as water pollution indices, this work shows that their ability indicating the water pollution is more limited than other indices. In contrast, strong correlations between SI and chemical oxygen demand, electric conductivity and other water conditions were observed. The superiority of the indices was also evaluated from the robustness of the indices using replicated samples, and it is concluded that SI is more robust than both BI and diversity indices.
Cells of Dimeregramma minus were cultivated in Petri dishes for some months. Valves were carrying one or two foliaceous processes standing nearby the ocelli in the rows of marginal processes. The expanded planes of those foliaceous processes are rather flat and spacious, and they are palaceous and connected to the vertical marginal processes which are as if their leafstalks.
The distribution of living terrestrial diatom communities is examined at 9 stations. The communities on soil and mosses are similar to each other. In all 91 taxa are distinguished. These taxa can be divided into two distinct groups based on the tolerance for desiccation. The group A is composed of species with high tolerance for desiccation and it indicates dry habitats. The group B consists of species which accompanied by the group A and recognized in both terrestrial and aquatic conditions. It is very useful to apply these terrestrial diatoms for palaeoenvironmental reconstructions.