| Arenaria norvegica | GB, VC112 Shetland, Shetland | Thomas B Edmondston | Botanical Society of London William Mateer | | SLBI |
| Arenaria norvegica | GB, VC112 Shetland, Shetland | Thomas Edmonston | Botanical Society of London Charles Cardale Babington George Stephen West William Mateer | 1846 | BIRM |
+ | Calamagrostis stricta | IE, VCH39 Co. Antrim, Lough Neagh | | Charles Bailey William Mateer | 6/1847 | MANCH |
+ | Calamagrostis stricta | IE, VCH39 Co. Antrim, Lough Neagh | William Mateer | Charles Bailey William Lowndes Notcutt | 6/1847 | MANCH |
| Callitriche brutia | IE, VCH38 Co. Down, Holywood | William Mateer | Donor Unknown William Mateer | 7/1847 | BIRM |
| Callitriche hermaphroditica | IE, VCH39 Co. Antrim, Antrim | William Mateer | Harold Stuart Thompson Thomas Clark | | BIRM |
+ | Carex buxbaumii | IE, VCH39 Co. Antrim, Lough Neagh | William Mateer | Charles Bailey | | MANCH |
| Carex canescens | IE, VCH38 Co. Down, Knockbreda | William Mateer | Frederick Janson Hanbury John Thomas Irvine Boswell-Syme William Mateer | 6/1849 | BM |
| Carex canescens | IE, VCH39 Co. Antrim, Lough Neagh | William Mateer | John Thomas Irvine Boswell-Syme Frederick Janson Hanbury | 7/1849 | BM |
| Carex nigra | IE, VCH39 Co. Antrim, Lough Neagh | William Mateer | Harold Stuart Thompson Thomas Clark | 7/1849 | BIRM |
| Elatine hexandra | IE, VCH39 Co. Antrim, Lagan Canal | William Mateer | Augustin Ley | 8/1847 | BIRM |
| Elatine hydropiper | IE, VCH39 Co. Antrim, Belfast,Lagan Canal | William Mateer | George Stephen West | 8/1847 | BIRM |
| Elatine hydropiper | IE, VCH39 Co. Antrim, Lagan Canal | William Mateer | Allan Octavian Hume William Mateer | 8/1847 | SLBI |
| Elatine hydropiper | IE, VCH39 Co. Antrim, Lagan Canal | William Mateer | Harold Stuart Thompson Thomas Clark | 8/1847 | BIRM |
| Equisetum hyemale | IE, VCH39 Co. Antrim, Divis, Crow Glen | William Mateer | Harold Stuart Thompson Thomas Clark William Mateer | 5/1847 | BIRM |
+ | Equisetum hyemale x variegatum = E. x trachyodon | IE, VCH39 Co. Antrim, Belfast,Colin Glen | William Mateer | Charles Bailey | 8/1850 | MANCH |
+ | Equisetum hyemale x variegatum = E. x trachyodon | IE, VCH39 Co. Antrim, Belfast,Colin Glen | William Mateer | John Ray Hardy | 7/1847 | MANCH |
+ | Equisetum hyemale x variegatum = E. x trachyodon | IE, VCH39 Co. Antrim, Belfast,Colin Glen | William Mateer | | 5/1846 | MANCH |
| Equisetum hyemale x variegatum = E. x trachyodon | IE, VCH39 Co. Antrim, Colin Glen | William Mateer | Harold Stuart Thompson Thomas Clark William Mateer | 5/1847 | BIRM |
| Equisetum palustre | IE, VCH38,VCH39, Lagan Canal | | Charles Ottley Groom William Mateer | 6/1847 | BON |
| Equisetum variegatum | IE, VCH39 Co. Antrim, Colin Glen | William Mateer | Mantua And Montferrat | 7/1847 | BON |
+ | Gentianella campestris | IE, VCH39 Co. Antrim, Wolf Hill | William Mateer | Charles Bailey William Lowndes Notcutt | 8/1847 | MANCH |
| Mimulus guttatus | IE, VCH38 Co. Down, Charlyville Glen | William Mateer | | 7/1846 | SLBI |
| Orobanche alba | IE, VCH39 Co. Antrim, Cave Hill, Belfast | William Mateer | Thomas Clark William Mateer | 7/1847 | BIRM |
| Polygala vulgaris subsp. collina | IE, VCH38 Co. Down, Maghera | William Mateer | Harold Stuart Thompson Thomas Clark | 6/1848 | BIRM |
| Polygala vulgaris subsp. collina | IE, VCH38 Co. Down, Mullagh | William Mateer | Harold Stuart Thompson Thomas Clark | 6/1849 | BIRM |
| Polystichum setiferum | IE, VCH39 Co. Antrim, Colin Glen | William Mateer | Harold Stuart Thompson Thomas Clark William Mateer | 7/1847 | BIRM |
| Potamogeton natans | IE, VCH39 Co. Antrim | William Mateer | Hewett Cottrell Watson | 7/1846 | MANCH |
| Suaeda maritima | IE, VCH38 Co. Down, Holywood | William Mateer | Harold Stuart Thompson | 7/1847 | BIRM |
| Veronica alpina | GB, Ambiguous locality (GB), Clova | McNab | Harold Stuart Thompson Thomas Clark William Mateer | 2/8/1831 | BIRM |