| Vicia parviflora | GB, VC13 West Sussex, Heyshott | Iolo Aneurin Williams | | 7/1924 | SLBI |
| Veronica beccabunga | GB, VC113 Channel Islands, Jersey | Iolo Aneurin Williams | | 25/8/1930 | K |
| Veronica beccabunga | GB, VC113 Channel Islands, Pont Marquet | Iolo Aneurin Williams | | 25/8/1930 | K |
| Veronica beccabunga | GB, VC113 Channel Islands, Pont Marquet | Iolo Aneurin Williams | | 25/8/1930 | K |
| Veronica agrestis | GB, VC20 Hertfordshire, Tring Station | Iolo Aneurin Williams | Watson Botanical Exchange Club Job Edward Lousley | 5/10/1928 | SLBI |
| Veronica agrestis | GB, VC20 Hertfordshire, Tring Station | Iolo Aneurin Williams | Watson Botanical Exchange Club J Fraser | 5/10/1928 | K |
| Trifolium arvense | GB, VC29 Cambridgeshire, Furze Hills | Iolo Aneurin Williams | Watson Botanical Exchange Club | 8/7/1926 | SLBI |
| Symphytum officinale x asperum = S. x uplandicum | GB, VC17 Surrey, Haslemere | Iolo Aneurin Williams | Watson Botanical Exchange Club | 24/6/1925 | SLBI |
| Sisymbrium pannonicum | GB, VC17 Surrey, Thursley | Iolo Aneurin Williams | | 9/1924 | SLBI |
| Sisymbrium officinale | GB, VC24 Buckinghamshire, Slough | Iolo Aneurin Williams | Botanical Exchange Club of The British Isles Job Edward Lousley | 23/7/1927 | SLBI |
| Senecio viscosus | GB, VC21 Middlesex, Chelsea | Iolo Aneurin Williams | | 5/8/1924 | SLBI |
| Salix fragilis x triandra = S. x alopecuroides | GB, VC17 Surrey, Haslemere | Iolo Aneurin Williams | Watson Botanical Exchange Club | 23/5/1925 | SLBI |
| Sagina boydii subsp. apetala | GB, VC113 Channel Islands, Guernsey, Cobo Bay | Iolo Aneurin Williams | Botanical Exchange Club of The British Isles Harold Stuart Thompson | 8/6/1928 | BIRM |
| Ranunculus peltatus | GB, VC17 Surrey, Chiddingfold | Iolo Aneurin Williams | Watson Botanical Exchange Club | 28/5/1927 | SLBI |
| Ranunculus peltatus | GB, VC17 Surrey, Ramsnest | Iolo Aneurin Williams | Watson Botanical Exchange Club Iolo Aneurin Williams William Harold Pearsall | 28/5/1927 | SLBI |
| Ranunculus peltatus | GB, VC17 Surrey, Ramsnest | Iolo Aneurin Williams | | 28/5/1927 | SLBI |
| Ranunculus peltatus | GB, VC17 Surrey, Ramsnest | Iolo Aneurin Williams | Watson Botanical Exchange Club Harold Stuart Thompson | 28/5/1927 | BIRM |
| Ranunculus omiophyllus x peltatus = R. x hiltonii | GB, VC14 East Sussex, Copthorne | Iolo Aneurin Williams | Watson Botanical Exchange Club | 27/3/1926 | SLBI |
+ | Ranunculus omiophyllus x peltatus = R. x hiltonii | GB, VC14 East Sussex, Copthorne | Iolo Aneurin Williams | | 27/3/1926 | BIRM |
| Potamogeton polygonifolius | GB, VC17 Surrey, Thursley | Iolo Aneurin Williams | Watson Botanical Exchange Club | 27/6/1925 | SLBI |
| Potamogeton polygonifolius | GB, VC17 Surrey, Thursley | Iolo Aneurin Williams | Watson Botanical Exchange Club | 11/1924 | SLBI |
| Potamogeton polygonifolius | GB, VC17 Surrey, Thursley | Iolo Aneurin Williams | Watson Botanical Exchange Club Harold Stuart Thompson | 11/1924 | BIRM |
| Potamogeton polygonifolius | GB, VC17 Surrey, Thursley | Iolo Aneurin Williams | Watson Botanical Exchange Club Harold Stuart Thompson | 27/6/1925 | BIRM |
| Potamogeton polygonifolius | GB, VC108 West Sutherland, Durness | Iolo Aneurin Williams | | 6/9/1955 | E |
| Potamogeton polygonifolius | GB, VC112 Shetland, Fair Isle | Iolo Aneurin Williams | The British Museum | 27/9/1956 | E |
| Potamogeton polygonifolius | GB, VC112 Shetland, Loch of Cliff | Iolo Aneurin Williams | The British Museum | 2/7/1948 | E |
| Potamogeton natans | GB, VC108 West Sutherland, Altnaharra | Iolo Aneurin Williams | The British Museum | 3/9/1955 | E |
| Potamogeton natans | GB, VC110 Outer Hebrides, Loch Druidibeg | Iolo Aneurin Williams | The British Museum | 20/6/1958 | E |
| Potamogeton gramineus | GB, VC108 West Sutherland, Loch Caladail | Iolo Aneurin Williams | The British Museum | 4/9/1955 | E |
| Potamogeton gramineus | GB, VC110 Outer Hebrides, Loch Druidibeg | Iolo Aneurin Williams | | 20/6/1958 | E |
| Misopates orontium | GB, VC17 Surrey, Byfleet | Iolo Aneurin Williams John Scott Lennox Gilmour William Bertram Turrill | | 25/9/1934 | K |
| Mercurialis perennis | GB, VC17 Surrey, Thursley | Iolo Aneurin Williams | Watson Botanical Exchange Club | 22/4/1926 | SLBI |
| Mentha arvensis | GB, VC11 South Hampshire, Ringwood | Iolo Aneurin Williams | Watson Botanical Exchange Club | 1/8/1929 | SLBI |
| Mentha arvensis | GB, VC11 South Hampshire, Ringwood | Iolo Aneurin Williams | Watson Botanical Exchange Club Job Edward Lousley | 1/8/1929 | SLBI |
| Medicago sativa subsp. falcata | GB, VC24 Buckinghamshire, Slough | Iolo Aneurin Williams | Botanical Exchange Club of The British Isles Job Edward Lousley | 1/10/1927 | SLBI |
| Medicago polymorpha | GB, VC3 South Devon, Dawlish | Iolo Aneurin Williams | Botanical Exchange Club of The British Isles | 1/9/1927 | SLBI |
| Medicago polymorpha | GB, VC3 South Devon, Dawlish Warren | Iolo Aneurin Williams | Botanical Exchange Club of The British Isles | 15/9/1927 | SLBI |
| Leontodon autumnalis | GB, VC1 West Cornwall, Ruan Pool | Iolo Aneurin Williams | Watson Botanical Exchange Club | 2/9/1925 | SLBI |
| Inula crithmoides | GB, VC11 South Hampshire, Hayling Island | Iolo Aneurin Williams | Watson Botanical Exchange Club Job Edward Lousley | 26/8/1926 | SLBI |
| Ilex aquifolium | GB, VC20 Hertfordshire, Berkhampstead | Iolo Aneurin Williams | Watson Botanical Exchange Club | 25/2/1928 | SLBI |