Unusual cell structures in tumor-like formations of Gracilaria (Rhodophyta).

This paper deals with electron microscopic observations on cultivated plants of the marine red alga Gracilaria verrucosa which developed simple galla; also sea collected material, without galls, had been studied. The galls showed unusual but characteristic cell structured, caterpillar-like bodies, containing rows of fusiform bodies. These were found mostly in the cytoplasm near the plastids, in one case connected with the endoplasmic reticulum, occasionally even inside the nucleus, and are described here, as far as we know, for the first time. It does not seem probably that the caterpillar-like bodies represent mitochondria or bacteria, but the hypothesis that fusiform bodies are related to virus-like structures is discussed. The normal tissues as well as the gall tissue of the laboratory plants contained, besides plastids typical for the red algae, another type of plastids characterized by tubular thylakoids.