budding in the upper end of the ([a.sub.1]) hydranth below the capitulum (Figure 2B).
Crawford, "The fine structure of the frustule
of melosira varians C.
Diatomaceous earth, also known as diatomite, is a fossil material of sedimentary origin, formed over centuries by siliceous skeleton (called "frustule
") of aquatic unicellular microalgae, the diatoms, deposited on bottom of lakes or present in marine environments.
The most striking feature of the diatom is its elaborate frustule
made up of grotesque amorphous silicon.
Cell solitary frustule
twisted along the apical axis, panduriform; keeled raphe in each valve; plastids two and large.
Natural counting units were defined as one unit for each colony, filament, diatom frustule
(regardless if colonial or filamentous) or unicellular algae.
samples for microscope analysis were processed according to Parsons et al.
Features Observed Weber (1970) Chloroplast 1-2 several Frustule
diameter ([micro]m) 3-4,5 3-4 Pervalvar axis ([micro]m) 6-10 4-8 Areolae in 10 [micro]m 8 - Number of processes 5 -7 5-8 Rimoportula 1 - Features Hasle & Evensen Belcher & Swale (1976) (1978) Chloroplast Frustule
diameter ([micro]m) 1-2 (4) 1-2 Pervalvar axis ([micro]m) 3-4 3-4 Areolae in 10 [micro]m - 6-10 Number of processes - 8 Rimoportula 6-8 5-6 1 1
Diatoms are a unique algal group because they are surrounded by a hard, silica-rich shell called a frustule
that often has an incredibly intricate and delicate structure.