So far this is the best pubblication I found on the Charophyceae of Europe.

There are also other more recent pubblications, but they are on specific countries.

Any other suggestion?

http://gallica.bnf.fr/ark:/12148/bpt6k6569159t/f1.image

Here is a new one, but I have not had time to check it yet.

Polish Charophytes. An illustrated guide to identification. 2014. ca. 300 col. photogr. 120 p. 4to. Paper bd. - In English.

https://koeltz.com/product.aspx?pid=208544

Thank you very much Nataliya.

Probably this could also help you:

https://www.researchgate.net/publication/249442243_TAXONOMIC_REEXAMINATION_OF_CHARA_GLOBULARIS_%28CHARALES_CHAROPHYCEAE%29_FROM_JAPAN_BASED_ON_OOSPORE_MORPHOLOGY_AND_rbc_L_GENE_SEQUENCES_AND_THE_DESCRIPTION_OF_C._LEPTOSPORA_SP._NOV

Article Taxonomic reexamination of chara globularis (charales, charo...

 Since Corillion 1957, there has been a new publication in french from Corillion 1975

Corillion R., 1975 - Flore et végétation du Massif Armoricain.T. IV. Flore des Charophytes (Characées) du Massif Armoricain et des contrées voisines d'Europe occidentale.Jouve ed., Paris. 216 p.

But you also have 

Cirujano S., Cambra J., Sânchez Castillo P.M., Meco A. & Flor Arnau N., 2007 - Flora ibérica. Algas continentales. Carôfitos (Characeae). Pieal Jardin Botânico de

Madrid. 132 p

https://www.chsegura.es/export/descargas/informaciongeneral/mediatecadigital/libros/docsdescarga/0134-Flora-Iberica.Algas-Continentales.Carofitos-Characeae.pdf

Hello Matteo,

This year, a new flore was published, look this publication, for 12€ you have lot of species !

http://www.oncfs.gouv.fr/Espace-Presse-Actualites-ru16/Guide-des-characees-de-France-mediterraneenne-news1833

http://www.oncfs.gouv.fr/IMG/file/publications/bon_de_commande_Guide_Characees_english.pdf

Yann

Dear Yann,

thank you very much!!

Matteo

Dear Matteo,

If you want, you can download 3 files about characeae on my RG profile, identification criteria and macro-microphoto of characeae. It's in french but you have latin name for all species.

Warning : We have to reconsider the identification of Chara hispida in chara polyacantha.

Yann

Pas de problème avec le français.

Merci encore.

Matteo