This class of soups may be called Purees.
For instance, Palestine soup is really a puree of Jerusalem artichokes; ordinary pea soup is a puree of split peas.

In making our ordinary vegetarian soups of all kinds, as a rule, all the ingredients should be rubbed through a sieve.

The economy of this is obvious on the face of it.
In the case of thickening soup by means of some kinds of flour, for richness and flavour there is nothing to equal ordinary flour that has been cooked.

This is what Frenchmen call roux.
As white and brown roux are the very backbone of vegetarian cookery a few words of explanation may not be out of place.

On referring to the recipe for making white and brown roux, it will be seen that it is simply flour cooked by means of frying it in butter, In white roux each grain of flour is cooked till it is done.