S. tectorum v. alpinum - in general

S. tectorum var. alpinum was first described by Grisebach & Schenk in 1852. Praeger described the specie later.

Synonims are:
S. boutignyanum Billot & Grenier
S. arvernense form boutignyanum Rouy & Camus

It is a small and neat-growing plant of the mountains, found in
- the Pyrenees,
- especially common in the northern and central Alps
- Istria (Istria - penninsula - is partly in Slovenia, partly in Croatia!).

Rosettes are 2 to 6 cm in diameter with green leaves that are always reddish at the base, with or without a purple-brown leaf tips. Flower stems 10 to 30 cm high, inflorescence is compact and flattish.

S. tectorum alpinum is a synonym of S. tectorum tectorum (Alps)
S. tectorum boutignyanum is a valid sub species of S. tectorum (Pyrenees)
S. arvernense is a valid species (or a sub species of S. tectorum. In this case => S. tectorum arvernense) from Massif Central, France

Am I understanding correct that Sempervivum (t) schotti a synonim is of S. tectorum v. alpinum?

Does anyone know what the supposed differences were on basis of which "schotti" was once described as a different taxon?

Welcome illustrator !

According to Gerard Dumont, Sempervivum schottii Baker (non C.B.Lehm. & Schnittsp.) is a synonym of Sempervivum tectorum subsp. tectorum var. acuminatum (Schott) Fiori.
See here (in french):
http://stalikez.info/fsm/semp/1mk.php

Sempervivum ×schottii C.B.Lehm. & Schnittsp. is a hybrid between S. tectorum and S. montanum
See here: http://stalikez.info/fsm/semp/5i.php

Ok, that clarifies it.