From Zürich airport to Zürich HB (Main Station)
Zürich airport has its own railway station called Zürich Flughafen. The route to Zürich City is part of ZVV, the public transport network of Zürich, zones 10 and 21. The tickets are valid for all public transport within these zones, let it be train, tram, bus, or boat. In particular, as zone 10 includes the city of Zürich, these tickets are also valid for tram or bus that takes you from Zürich HB to the Institute.
A taxi from Zurich Airport to the city should cost about CHF 50-60 (€30-40).
From Zurich HB (Main Station) to the Institute of Systematic Botany
The tram stations closest to the Institute are called Höschgasse (tram #2, 4), Hegibachplatz (tram #11), or Botanischer Garten (bus #33; map). Tram number 4 and 11 take you directly from Zurich HB to the Institute.
In case you come from Zurich airport by train, your ticket is also valid for the tram trip. Otherwise, your train ticket is most likely not valid for public transport within Zurich and you have to buy a ticket at one of the blue ticket machines.
Tram 4 (heading to Tiefenbrunnen) takes you directly from Zürich HB to Höschgasse. If you arrive at Zürich HB, go to the station hall and turn towards the large ad-board, following the signs towards Bahnhofquai/Hauptbahnhof. From tram stop Höschgasse a white signpost "Botanischer Garten" leads you to the Botanic Gardens and the Institute.
Tram 11 (heading to Rehalp) takes you directly from Zürich HB to Hegibachplatz. If you arrive at Zürich HB, go to the station hall and turn towards the large ad-board, following the signs towards Bahnhofstrasse to get to the tram stop.
You can reach the Institute on foot, if your hotel is situated in close proximity.