By these procedures a lot of information is missed concerning the chloroplasts and also information about diatoms living in colonies.
Diatoms are basically unicellular.
However, many species use several methods to stay together. It is simplest to stay together after dividing, by means of mechanical means or by sticking together by some sort of paste. Other methods are to stay together by making a common tube or by by a string that holds the cells together. So colonies can be formed by siliceous structures, for instance by spines. Examples are Biddulphia species.