| Mentha aquatica x spicata = M. x piperita | IE, VCH39 Co. Antrim, Carnmoney | Samuel Alexander Stewart | Science & Art Museum Dublin | 12/8/1893 | DBN |
| Mentha aquatica x spicata = M. x piperita | IE, VCH39 Co. Antrim, Masserine Park | Samuel Alexander Stewart | | 2/8/1885 | DBN |
| Mentha arvensis x aquatica = M. x verticillata | IE, VCH38 Co. Down, Saul | Samuel Alexander Stewart | | 8/1897 | DBN |
| Carex distans | IE, VCH39 Co. Antrim, Black Head | Samuel Alexander Stewart | | 29/6/1872 | BON |
| Equisetum hyemale x variegatum = E. x trachyodon | IE, VCH39 Co. Antrim, Colin Glen | Samuel Alexander Stewart | | 1/7/1872 | BON |
| Eriocaulon aquaticum | IE, VCH16 West Galway, Roundstone | Samuel Alexander Stewart | | 29/7/1867 | BON |
| Carex arenaria | IE, VCH38 Co. Down | Samuel Alexander Stewart | Botanical Exchange Club of The British Isles Frederick Janson Hanbury | 6/1876 | BM |
| Carex arenaria | IE, VCH38 Co. Down | Samuel Alexander Stewart | Edward Francis Linton | 6/1876 | BM |
| Carex dioica | IE, VCH39 Co. Antrim, Divis Hill | Samuel Alexander Stewart | | 12/5/1866 | BM |
| Carex remota | IE, VCH39 Co. Antrim, Cushendall | Samuel Alexander Stewart | | 28/6/1866 | BM |
| Carex spicata | IE, VCH39 Co. Antrim, Greencastle | Samuel Alexander Stewart | Edward Francis Linton | 19/6/1873 | BM |
| Adiantum capillus-veneris | IE, VCH9 Co. Clare, Black Head | Samuel Alexander Stewart | Botanical Exchange Club of The British Isles Augustin Ley Samuel Alexander Stewart | 15/7/1878 | BIRM |
| Apium nodiflorum x inundatum = A. x moorei | IE, VCH16 West Galway, Doonpatrick | Samuel Alexander Stewart | Samuel Alexander Stewart | 7/1880 | BIRM |
| Apium nodiflorum x inundatum = A. x moorei | IE, VCH38 Co. Down, Downpatrick,Quoile | Samuel Alexander Stewart | Botanical Exchange Club of The British Isles Augustin Ley | 7/1880 | BIRM |
| Arctostaphylos uva-ursi | IE, VCH9 Co. Clare, Black Head | Samuel Alexander Stewart | Augustin Ley | 13/5/1876 | BIRM |
| Arctostaphylos uva-ursi | IE, VCH9 Co. Clare, Black Head | Samuel Alexander Stewart | Robert Large Baker | 5/1876 | BIRM |
| Arenaria ciliata | IE, VCH28 Co. Sligo, Kings Mountain | Samuel Alexander Stewart | Botanical Exchange Club of The British Isles Charles Bailey | 18/7/1879 | BIRM |
| Arenaria ciliata | IE, VCH28 Co. Sligo, Kings Mountain | Samuel Alexander Stewart | Botanical Exchange Club of The British Isles Augustin Ley | 18/7/1879 | BIRM |
| Atriplex laciniata | IE, VCH38 Co. Down, Groomport | Samuel Alexander Stewart | Augustin Ley | 10/9/1870 | BIRM |
| Barbarea intermedia | IE, VCH39 Co. Antrim, Whitewell, Belfast | Samuel Alexander Stewart | Botanical Exchange Club of The British Isles Augustin Ley | 15/6/1879 | BIRM |
| Bidens cernua | IE, VCH39 Co. Antrim, Portmore Lough | Samuel Alexander Stewart | Botanical Exchange Club of The British Isles Augustin Ley | 27/8/1886 | BIRM |
| Callitriche hamulata | IE, VCH38 Co. Down, Castlewellan Forest Park | Samuel Alexander Stewart | Watson Botanical Exchange Club Coslett Herbert Waddell Harold Stuart Thompson | 7/6/1897 | BIRM |
| Carex arenaria | IE, VCH38 Co. Down, Co. Down | Samuel Alexander Stewart | Botanical Exchange Club of The British Isles Augustin Ley | 6/1876 | BIRM |
| Carex elata | IE, VCH39 Co. Antrim, Portmore | Samuel Alexander Stewart | Augustin Ley | 20/6/1872 | BIRM |
| Daboecia cantabrica | IE, Mayo, Uggool | Samuel Alexander Stewart | Robert Large Baker | 19/8/1877 | BIRM |
| Equisetum hyemale x variegatum = E. x trachyodon | IE, VCH39 Co. Antrim, Belfast,Colin Glen | Samuel Alexander Stewart | Harold Stuart Thompson | 22/6/1879 | BIRM |
| Equisetum hyemale x variegatum = E. x trachyodon | IE, VCH39 Co. Antrim, Colin Glen | Samuel Alexander Stewart | Augustin Ley | 1/7/1872 | BIRM |
| Equisetum hyemale x variegatum = E. x trachyodon | IE, VCH39 Co. Antrim, Colin Glen | Samuel Alexander Stewart | Botanical Exchange Club of The British Isles Augustin Ley | 29/7/1893 | BIRM |
+ | Equisetum hyemale x variegatum = E. x trachyodon | IE, VCH39 Co. Antrim, Colin Glen | Samuel Alexander Stewart | | 22/6/1879 | BIRM |
| Equisetum variegatum | IE, VCH19,VCH22, Maynooth | Samuel Alexander Stewart | Augustin Ley | 15/5/1876 | BIRM |
| Euphorbia hyberna | IE, VCH2 North Kerry, Killarney,Cromagloun (Cromaglan) | Samuel Alexander Stewart | Botanical Exchange Club of The British Isles Augustin Ley | 15/6/1885 | BIRM |
+ | Hieracium basalticola | IE, VCH39 Co. Antrim, Sallagh Braes | Samuel Alexander Stewart | | 15/6/1890 | BIRM |
| Melampyrum sylvaticum | IE, VCH38,VCH39, Belfast | Samuel Alexander Stewart | Augustin Ley | 12/6/1872 | BIRM |
| Najas flexilis | IE, VCH16 West Galway, Roundstone | Samuel Alexander Stewart | Augustin Ley | 15/8/1877 | BIRM |
| Najas flexilis | IE, VCH16 West Galway, Roundstone | Samuel Alexander Stewart | Harold Stuart Thompson | 15/8/1877 | BIRM |
| Orobanche alba | IE, VCH39 Co. Antrim, Cave Hill, Belfast | Samuel Alexander Stewart | Augustin Ley | 8/7/1871 | BIRM |
| Pinguicula grandiflora | IE, VCH1 South Kerry, Mangerton | Samuel Alexander Stewart | Botanical Exchange Club of The British Isles Augustin Ley | 25/6/1885 | BIRM |
| Polygala vulgaris | IE, VCH28 Co. Sligo, Benbulben | Samuel Alexander Stewart | Botanical Exchange Club of The British Isles Augustin Ley | 16/7/1879 | BIRM |
+ | Potamogeton perfoliatus x crispus = P. x cooperi | IE, VCH39 Co. Antrim, Sixmile River above Templepatrick | Samuel Alexander Stewart | | 10/8/1894 | BIRM |
| Potamogeton perfoliatus x crispus = P. x cooperi | IE, VCH39 Co. Antrim, Templepatrick | Samuel Alexander Stewart | Botanical Exchange Club of The British Isles Augustin Ley | 10/8/1894 | BIRM |