| Acer campestre var. leiocarpum | GB, VC12 North Hampshire, Ashmansworth | William Charles Barton | Watson Botanical Exchange Club | 18/9/1914 | SLBI |
| Aconitum napellus | GB, VC17 Surrey, Peper Harow | Rowland John Burdon | Watson Botanical Exchange Club | 22/6/1926 | SLBI |
| Acorus calamus | GB, VC21 Middlesex, Walton Bridge | Edward Charles Wallace | Watson Botanical Exchange Club Edward Charles Wallace | 1/7/1928 | SLBI |
| Aethusa cynapium subsp. agrestis | GB, VC29 Cambridgeshire, Dernford Farm | Albert John Crosfield | Watson Botanical Exchange Club | 19/9/1923 | SLBI |
| Agrimonia eupatoria | GB, VC20 Hertfordshire, Sacomb | Joseph Edward Little | Watson Botanical Exchange Club | 8/1929 to 9/1929 | SLBI |
| Agrimonia procera | GB, VC13 West Sussex, Fishbourne | Joseph Edward Little Rowland John Burdon | Watson Botanical Exchange Club | 8/10/1918 | SLBI |
| Agrimonia procera | GB, VC13 West Sussex, Blackdown | Joseph Edward Little | Watson Botanical Exchange Club | 8/1929 | SLBI |
| Ajuga chamaepitys | GB, VC30,VC20, Tingley Wood | Joseph Edward Little | Watson Botanical Exchange Club | 7/1909 6/1929 | SLBI |
| Ajuga chamaepitys | GB, VC17 Surrey, Chipstead | Job Edward Lousley | Watson Botanical Exchange Club Isaac A Helsby | 23/6/1923 | SLBI |
| Ajuga chamaepitys | GB, VC20 Hertfordshire, TIngley Wood | Joseph Edward Little | Watson Botanical Exchange Club | 6/1929 to 7/1929 | K |
| Alchemilla glabra | GB, VC65 North-west Yorkshire, Jervaulx Abbey | Joseph Edward Little | Watson Botanical Exchange Club | 1/6/1925 | SLBI |
| Alchemilla vulgaris subsp. alpestris | GB, VC69 Westmorland, Grisedale Pass | Albert John Crosfield | Watson Botanical Exchange Club Albert John Crosfield | 8/9/1897 | SHYB |
| Alisma lanceolatum | GB, VC29 Cambridgeshire, Burwell | Albert John Crosfield | Watson Botanical Exchange Club Albert John Crosfield | 8/9/1914 | SLBI |
| Allium carinatum | GB, VC84 West Lothian, Kirkliston, Carlowrie | McTaggert Cowan | Watson Botanical Exchange Club McTaggert Cowan | 12/8/1910 | SLBI |
| Allium carinatum | GB, VC17 Surrey, Croydon Cultivated GB, VC17 Surrey, Witley | Arthur Bennett | Watson Botanical Exchange Club | 8/1919 | SLBI |
| Allium carinatum | GB, VC17 Surrey, Witley Cultivated | Arthur Bennett | Watson Botanical Exchange Club | 8/1919 | SLBI |
| Allium ursinum | GB, VC5 South Somerset, Dunster | Edward Charles Wallace | Watson Botanical Exchange Club | 9/7/1929 | SLBI |
| Alnus glutinosa | GB, VC28 West Norfolk, Wallington Hall | Joseph Edward Little | Watson Botanical Exchange Club | 23/9/1927 | SLBI |
| Alnus glutinosa | GB, VC20 Hertfordshire, Ashbrook | Joseph Edward Little | Watson Botanical Exchange Club | 1/3/1927 | SLBI |
| Alnus incana | GB, VC20 Hertfordshire, Hitchin | Joseph Edward Little | Watson Botanical Exchange Club Joseph Edward Little | 28/7/1922 | SLBI |
| Amaranthus blitum | GB, VC14 East Sussex, Hastings | Leslie Beeching Hall | Watson Botanical Exchange Club Leslie Beeching Hall | 26/10/1921 | SLBI |
| Amaranthus retroflexus | GB, VC34 West Gloucestershire, Avonmouth Docks, Bristol | Ida Mary Roper | Watson Botanical Exchange Club | 19/8/1926 | SLBI |
| Amaranthus retroflexus | GB, VC16 West Kent, Tripcock Point | Henry Franklin Parsons | Watson Botanical Exchange Club Anthony Hurt Wolley Dod Henry Franklin Parsons | 18/8/1900 | SLBI |
| Anagallis arvensis | GB, VC52 Anglesey, Newborough Warren | Ida Mary Roper | Watson Botanical Exchange Club Ida Mary Roper | 28/8/1931 | SLBI |
| Anemone nemorosa | GB, VC1 West Cornwall, Ponsanooth | Ida Mary Roper | Watson Botanical Exchange Club Ida Mary Roper | 7/5/1931 | SLBI |
| Anisantha madritensis | GB, VC113 Channel Islands, L'Eree, Guernsey | Job Edward Lousley N A McCrea | Watson Botanical Exchange Club Job Edward Lousley | 15/6/1926 | BIRM |
| Anisantha tectorum | GB, VC6 North Somerset, Brislington | | Watson Botanical Exchange Club Ida Mary Roper | 21/5/1915 | BIRM |
| Anthyllis vulneraria | GB, VC13 West Sussex, Chichester | Rowland John Burdon | Watson Botanical Exchange Club | 4/6/1902 | SLBI |
| Anthyllis vulneraria var. coccinea | GB, VC1 West Cornwall, Lizard | Job Edward Lousley | Watson Botanical Exchange Club | 24/5/1928 | SLBI |
| Anthyllis vulneraria var. coccinea | GB, VC1 West Cornwall, Kynance | Job Edward Lousley | Watson Botanical Exchange Club | 25/5/1929 | SLBI |
| Arabis hirsuta | GB, VC17 Surrey, Epsom Cultivated IE, VCH16 West Galway, Roundstone,Dog's Bay | William Charles Barton | Watson Botanical Exchange Club William Charles Barton | 8/1918 | SLBI |
| Arctium minus | GB, VC20 Hertfordshire, Gt Wymondley Springs | Joseph Edward Little | Watson Botanical Exchange Club Job Edward Lousley | 22/9/1926 | SLBI |
| Artemisia campestris | GB, VC28 West Norfolk, Cranwich | Joseph Edward Little | Watson Botanical Exchange Club | 10/10/1924 | SLBI |
| Artemisia campestris | GB, VC28 West Norfolk, Cranwich | Joseph Edward Little | Watson Botanical Exchange Club Job Edward Lousley | 10/10/1924 | SLBI |
| Artemisia stelleriana | GB, VC1 West Cornwall, Marazion | Frederick Hamilton Davey | Watson Botanical Exchange Club Frederick Hamilton Davey | 15/9/1906 | SLBI |
| Asplenium septentrionale | GB, VC49 Caernarvonshire, Llanrwst | John Edwards Griffith | Watson Botanical Exchange Club Albert John Crosfield | 8/1917 | BIRM |
| Aster linosyris | GB, VC3 South Devon, Berry Head | Anthony Hurt Wolley Dod | Watson Botanical Exchange Club Anthony Hurt Wolley Dod | 19/8/1909 | SLBI |
| Astragalus glycyphyllos | GB, VC6 North Somerset, Compton Dando | Ida Mary Roper | Watson Botanical Exchange Club Isaac A Helsby | 11/8/1925 | SLBI |
| Astragalus glycyphyllos | GB, VC6 North Somerset, Compton Dando | Ida Mary Roper | Watson Botanical Exchange Club Ida Mary Roper | 11/8/1925 | SLBI |
| Atriplex glabriuscula | GB, VC111 Orkney, Rousay | Mark Mckay | Watson Botanical Exchange Club Job Edward Lousley Henry Halcro Johnston | 5/10/1921 | SLBI |