Abstract
In this paper, a few observations on behaviour of mycelia of mulberry rust, Aecidium mori BARCLAY, in host tissue were described. The results obtained were as follows:
1. It could easily be found out that the primary infection was, distinctly in appearance, different from the secondary infection in symptoms of the disease. Namely, in the former case the disease was developed from the base of spring budding shoot infected last year, to every part of itself, in the later it was distributed somewhere on leaves, petioles, and younger portions of twigs. The author showed that each of these symptoms was caused by different process of mycelial growth (Fig. 1). In the primary infected shoot, the masses of mycelia grow at first near the vascular bundles of the shoot in parallel with them, and a little later the mycelia departed from the masses spread radially into the tissue around (Pl. I A, B). The mycelia reached just the under region of epidermis form the aecidia there (Pl. I B). Whereas, in the secondary infection, mycelia penetrating epidermic layer, spread gradually around the penetrated point (Pl. I C).
2. Mycelia growing in the intercellular spaces of the host tissue formed haustria in host cells (PI. F, G). Mycelial growth and formation of haustria were more abundant in the younger parenchyma of the host.
3. It may be possible that mycelia can use directly their food materials from sieve tube of the host. This is based on facts that in the primary infection in spring, mycelial growth is initiated along the vascular bundles, and in the secondary infection, only the residual mycelia are still alive around the vascular bundles in the neighbourhood of the necrotic tissues resulting from infection.
