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Anatomy
cell, forming the region of theca overlay. Extracellular organic coats envelop the plasma membrane
under the siliceous frustule. They exist in the form of both thick mucilaginous capsules and thin
tightly bound organic sheaths. The formation of the frustule occurs in the silica deposition vesicles,
derived from the Golgi apparatus. The vesicles eventually secrete their finished product onto the
cell surface in a precise position.
Diatoms can be divided artificially in centric and pennate according to the symmetry of their
frustule. In centric diatoms, the symmetry is radial, that is, the structure of the valve is arranged
in reference to a central point (Figure 2.9). However, within the centric series, there also oval,
FIGURE 2.8 Body scale of Mallomonas crassisquama.
FIGURE 2.9 Triceratium sp., a centric diatom.
Anatomy
cell, forming the region of theca overlay. Extracellular organic coats envelop the plasma membrane
under the siliceous frustule. They exist in the form of both thick mucilaginous capsules and thin
tightly bound organic sheaths. The formation of the frustule occurs in the silica deposition vesicles,
derived from the Golgi apparatus. The vesicles eventually secrete their finished product onto the
cell surface in a precise position.
Diatoms can be divided artificially in centric and pennate according to the symmetry of their
frustule. In centric diatoms, the symmetry is radial, that is, the structure of the valve is arranged
in reference to a central point (Figure 2.9). However, within the centric series, there also oval,
FIGURE 2.8 Body scale of Mallomonas crassisquama.
FIGURE 2.9 Triceratium sp., a centric diatom.