The anther usually consists of two fused thecae. There are five types of thecae ornamentation in this genus. The pollen is produced in four thecae on each anther. The pollen is produced in S-shaped thecae. The anthers contain a massive septum between the thecae that persists after anther dehiscence. Each daughter receives one of the parent cell's thecae, which becomes that cell's epitheca. The frustule forms as different sized valves, which overlap and are called thecae. Each stamen has two divergent, oblong and curved thecae. A characteristic of the genus includes one uniserial stipes with very elaborate thecae. A frustule is usually composed of two identically shaped but slightly differently sized thecae. The anthers are about in diameter and have divergent yellow thecae and purplish black connective. The typical anther is bilocular, i.e. it consists of two thecae. Stamen baculate to terete; thecae shorter than connective. The very large stamen numbers (20 to 40), are probably counts of thecae or microsporangia. A theca (plural thecae) refers to a sheath or a covering.