Diatoms of North AmericaGood question. There are not only an abundance of terms to describe the silicious parts of diatoms, but terms are often redundant and overlapping.
In the case of "process", the term is a general expression for fultoportula or rimoportula. "Process" could also be used for other structures that perforate the diatom valve like, carinoportula.
A ring of processes might refer to a ring of fultoportulae or of rimoportulae. And anyone could as easily say, "ring of fultoportulae", which might be more informative. Sometimes, however, we don't know what type of processes are present. For example, if the SEM structures of diatom has not been observed.
In older literature such as Round et al. (1990), fultoportulae are called "strutted processes" and rimoportulae are called "labiate processes".
In diatoms, fultoportulae function to secrete chitin fibrils. These tiny organic strands may function in buoyancy. They may also function in adsorption of nutrients, including metals. Rimoportulae secrete mucopolysaccarides. In some taxa, these materials join cells in colonies. In other taxa, they form stalks, or attach cells to surfaces.
