1) Excellent, illustrated pdf files for identifying species of Spartina that are weedy on the west coast of North America can be found by clicking here.
2) Dr. John Reeder has drawn my attention to some errors I (Mary Barkworth) made in the treatment of Spartina in FNA 25:
The generic treatment states that there are no lodicules in the genus. Reeder and Singh (1967) reported that their investigations of S. patens, S. pectinata, and S. spartinae show that all three species have "truncate vascularized lodicules, similar to those characteristic of eragrostoid-chloridoid grasses".
In addition, many of the chromosome counts that I listed for Spartina in FNA 25 appear to have been incorrect. They all came from a published course, but subsequent counts have cast dounbt on their accuracy. The base number for the genus is correctly stated as being x = 10. Despite this, many of the numbers listed were multiples of 7. I have listed more reliable counts below, together with their place of publication. Some were included in the FNA 25 account but it seems worthwhile to present all the information in one place..
Spartina anglica: 2n = 122 (Marchant 1963); 122, 124 (Marchant 1968a)
Spartina alterniflora: 2n = 62 (Marchant 1963, 1968b).
Spartina arundinacea: 2n = 40 (Marchant 1968b).
Spartina bakeri: 2n = 40 (Marchant 1968b).
Spartina cynosuroides: 2n = 40 (Marchant 1968b).
Spartina densiflora: 2n = 60 (Gerish 1979, as S. foliosa but probably S. densiflora, see Spicher and Josselyn 1985).
Spartina foliosa: 2n = 60 (Reeder 1984).
Spartina glabra: 2n = 62 (Marchant 1963, 1968b).
Spartina gracilis: 2n = 40 (Marchant 1968b; Reeder 1977).
Spartina maritima: 2n = 60 (Marchant 1963).
Spartina patens: 2n = 40 (Marchant 1968b; Reeder and Singh 1967).
Spartina pectinata: 2n = 40 (Marchant 1963, 1968b; Reeder 1977); 40 + 1 (Marchant 1963, 1968b); 80 (Reeder 1977).
Spartina spartinae: n = 20(Gould 1958, Reeder and Singh 1967).
Spartina ×townsendii: 2n = 62 (Marchant 1963); 60+2 (Marchant 1968a).