Date of this Version
There have been many systems of classification employed for the Bacillariaceæ, but very few of these have any valid claim, to be regarded as natural systems. They may be divided into three classes ; (1) those based on the structure of the valves, of which Kuetzing's, Prof. H. L. Smith's, and that employed by Kirchner are examples ; (2) those based on the form of the frond, the connecting membrane, and the gelatinous envelope, represented by Rev. Wm. Smith's ; and (3) those based on the structure of the endochrome and the manner of forming auxospores, represented by that of Paul Petit. The following is a brief outline of the systems mentioned.