These are plants that the CNPS Rare Plant Inventory says occur only in Marin.

Arctostaphylos montana ssp. montana
Arctostaphylos virgata
Calochortus tiburonensis
Ceanothus decornutus
Ceanothus gloriosus var. porrectus
Ceanothus masonii
Chorizanthe valida
Clarkia concinna ssp. raichei
Delphinium bakeri
Lessingia micradenia var. micradenia
Piperia elegans ssp. decurtata
Quercus parvula var. tamalpaisensis
Sidalcea hickmanii ssp. viridis
Stellaria littoralis
Streptanthus anomalus
Streptanthus batrachopus
Streptanthus glandulosus ssp. niger
Streptanthus glandulosus ssp. pulchellus

Refer to CNPS Rare Plant Inventory for Marin for more information about each species.