| RefNo | Title | Date |
| NLB/2/702 | Copy letter from Herbert Rix, to Professor Isaac Bayley Balfour, [Fellow of the Royal Society] | 15 October 1888 |
| NLB/3/204 | Copy letter from Herbert Rix, to Professor Isaac Balfour, Fellow of the Royal Society | 10 April 1889 |
| NLB/6/755 | Copy letter from Herbert Rix, to Professor Albert Julius Otto Penzig, Orto Botanico dell'Università di Genova | 8 July 1892 |
| NLB/6/736 | Copy letter from Herbert Rix, to Professor Harry Marshall Ward, Fellow of the Royal Society | 6 July 1892 |
| NLB/6/753 | Copy letter from Herbert Rix, to Professor Isaac Bayley Balfour, Fellow of the Royal Society | 8 July 1892 |
| NLB/29/524 | Copy letter from Robert William Frederick Harrison, to Professor Isaac Bayley Balfour, Fellow of the Royal Society | 31 October 1904 |
| NLB/8/140 | Copy letter from Theodore E James, to Professor Isaac Bayley Balfour, Fellow of the Royal Society | 20 July 1893 |
| RR/16/291 | Referee's report by Isaac Bayley Balfour, on a paper 'Further experiments & histological investigations on intumescences with observations on nuclear division in pathological tissues' by E Dale | May 1905 |
| NLB/14/688 | Copy letter from Robert William Frederick Harrison, to William Turner Thiselton-Dyer, Fellow of the Royal Society | 29 April 1895 |
| RR/16/22 | Referee's report by Isaac Bayley Balfour, on a paper 'Studies in the morphology of spore-producing members. No. V. general comparisons and conclusion' by Professor Frederick Orpen Bower | February 1903 |
| RR/16/87 | Referee's report by Isaac Bayley Balfour, on a paper 'The structure of the Palaeozoic seed Lagenostoma lomaxi with a statement of the evidence upon which it is referred to Lygingodendron' by Francis Wall Oliver and Dukinfield Henry Scott | March 1904 |
| NLB/15/157 | Copy letter from Robert William Frederick Harrison, to Professor Isaac Bayley Balfour, Fellow of the Royal Society | 7 July 1897 |
| NLB/15/233 | Copy letter from Robert William Frederick Harrison, to William Turner Thiselton-Dyer, Fellow of the Royal society | 21 July 1897 |
| NLB/15/287 | Copy letter from Robert William Frederick Harrison, to William Turner Thiselton-Dyer, Fellow of the Royal Society | 29 July 1897 |
| NLB/15/682 | Copy letter from Robert William Frederick Harrison, to William Turner Thiselton-Dyer, Fellow of the Royal Society | 16 November 1897 |
| NLB/20/22 | Copy letter from Robert William Frederick Harrison, to Professor Isaac Bayley Balfour, Fellow of the Royal Society | 16 January 1900 |
| NLB/20/32 | Copy letter from Robert William Frederick Harrison, to Professor Isaac Bayley Balfour, Fellow of the Royal Society | 19 January 1900 |
| NLB/21/775 | Copy letter from Robert William Frederick Harrison, to Professor Isaac Bayley Balfour, Fellow of the Royal Society | 28 January 1901 |
| NLB/25/89 | Copy letter from Robert William Frederick Harrison, to Professor Isaac Bayley Balfour, Fellow of the Royal Society | 6 August 1902 |
| NLB/28/518 | Copy letter from Robert William Frederick Harrison, to Professor Isaac Bayley Balfour, Fellow of the Royal Society | 22 March 1904 |
| NLB/33/665 | Copy letter from Robert William Frederick Harrison, to Professor Isaac Bayley Balfour, Fellow of the Royal Society | 17 October 1906 |
| NLB/35/598 | Copy letter from Robert William Frederick Harrison, to Professor Bayley Balfour, Fellow of the Royal Society | 18 June 1907 |
| NLB/34/586 | Copy letter from Robert William Frederick Harrison, to Professor Isaac Bayley Balfour, Fellow of the Royal Society | 11 February 1907 |
| NLB/34/732 | Copy letter from Robert William Frederick Harrison, to Professor Isaac Bayley Balfour, Fellow of the Royal Society | 4 March 1907 |
| NLB/34/744 | Copy letter from Robert William Frederick Harrison, to Professor Edward Bagnall Poulton, Fellow of the Royal Society | 5 March 1907 |
| NLB/40/401 | Copy letter from Robert William Frederick Harrison to Professor I [Issac] Bayley Balfour FRS | 3 June 1909 |
| NLB/43/61 | Copy letter from Robert William Frederick Harrison, to Professor [Issac] Bayley Balfour, Fellow of the Royal Society | 1 November 1910 |
| NLB/43/663 | Copy letter from Robert William Frederick Harrison, to Professor Issac Bayley Balfour, Fellow of the Royal Society | 6 March 1911 |
| RR/11/159 | Referee's report by Isaac Bayley Balfour, on a paper 'On Dischidia rafflesiana' by Percy Groom | 15 April 1873 |
| RR/9/200 | Referee's report by Isaac Bayley Balfour, on a paper 'On the comparative morphology of the leaf the vascular cryptogams and gymnosperms' by Frederick Orpen Bower | 4 September 1884 |
| RR/9/254 | Referee's report by Isaac Bayley Balfour, on a paper 'On the development and morphology of phylloglossum drummondii' by Frederick Orpen Bower | 20 August 1885 |
| RR/10/107 | Referee's report by Isaac Bayley Balfour, on a paper 'On the tubercular swellings on the roots of Vicia faba' by Harry Marshall Ward | 12 August 1887 |
| RR/9/416 | Referee's report by Isaac Bayley Balfour, on a paper 'On the structure and life-history of Entyloma Ranunculi (bonorden)' by Harry Marshall Ward | 20 December 1886 |
| RR/13/188 | Letter from Robert Harrison, Assistant Secretary of the Royal Society, on a paper 'On the leaves of lathraea squamaria' by Percy Groom to William Turner Thiselton-Dyer | 29 April 1897 |
| RR/13/169 | Referee's report by Isaac Bayley Balfour, on a paper 'Studies in the morphology of spore-producing members.—III. Marattiaceæ' by Frederick Orpen Bower | July 1897 |
| RR/14/119 | Referee's report by Isaac Bayley Balfour, on a paper 'Studies in the morphology of spore-producing members.—No. IV. The leptosporangiate ferns' by Frederick Orpen Bower | nd [May 1899] |
| RR/17/41 | Referee's report by Isaac Bayley Balfour, on a paper 'On the anatomy of the Julianiaceae considered from the systematic point of view' by Felix Eugen Fritsch | [March 1907] |
| RR/14/137 | Referee's report by Isaac Bayley Balfour, on a paper 'Further observations on the nature and functions of the nodules of leguminous plants' by Maria Dawson | nd [February 1900] |
| RR/17/49 | Referee's report by Isaac Bayley Balfour, on a paper 'On the Julianiaceae: a new natural order of plants' by William Botting Hemsley | [October 1906] |
| RR/13/187 | Referee's report by Isaac Bayley Balfour, on a paper 'On the leaves of lathraea squamaria' by Percy Groom | 28 April 1897 |
| RR/13/265 | Referee's report by Isaac Bayley Balfour, on a paper 'On the structure and affinities of fossil plants from the palæozoic rocks.— II. On spencerites, a new genus of lycopodiaceous cones from the coal measures, founded on the lepidodendron spenceri of Williamson' by Henry Dukinfield Scott | November 1897 |
| RR/15/27 | Referee's report by Isaac Bayley Balfour, on a paper 'Investigation on the abnormal outgrowths or intumescences on hibuscus vitifolious, Linn: A study in experimental plant pathology' by Elizabeth Dale | February 1901 |
| NLB/57/379 | Copy letter from Robert William Frederick Harrison, Assistant Secretary of the Royal Society; to Professor I [Isaac] Bayley Balfour, FRS | 29 October 1919 |
| NLB/66/153 | Copy letter from Francis Alexander Towle, Assistant Secretary and Librarian of the Royal Society; to the Librarian of the Royal Botanic Garden, Edinburgh | 5 March 1924 |
| EC/1884/08 | Balfour, Sir Isaac Bayley: certificate of election to the Royal Society | |
| IM/Maull/000216 | Balfour, Isaac Bayley | nd |
| NLB/15/560 | Copy letter from Arthur Wiliam Rucker, to Mr Osbert Salvin, [Fellow of the Royal Society] | 28 October 1897 |
| RR/10/177 | Referee's report by Isaac Bayley Balfour, on a paper 'A contribution to the study of the comparative anatomy of flowers' by G Henslow | 2 February 1888 |
| RR/12/266 | Referee's report by Isaac Bayley Balfour, on a paper 'Further observations on the organization of the fossil plants of the coal- measures. —Part I. Calamites, Calamostachys, and Sphenophyllum' by William Crawford Williamson and Dukinfield Henry Scott | 16 April 1894 |
| RR/12/407 | Referee's report by Isaac Bayley Balfour, on a paper 'Further observations on the organization of the fossil plants of the coal-measures.—Part II. The roots of Calamites' by William Crawford Williamson and Dukinfield Henry Scott | 3 April 1895 |
| MC/13/60 | Letter from [Isaac] Bayley Balfour, Glasgow University, to Professor [George Gabriel] Stokes, [Secretary of the Royal Society] | 14 June 1884 |
| MC/13 | Volume 13 of miscellaneous correspondence regarding business matters, sent to the Royal Society | 1884 |
| RR/12/410 | Referee's report by Isaac Bayley Balfour, on a paper 'Further observations on the organization of the fossil plants of the coal-measures.-Part III. Lygnodendron and Heterangium' by William Crawford Williamson and Dukinfield Henry Scott | 29 July 1895 |
| RR/13/264 | Letter from Robert Harrison, Assistant Secretary of the Royal Society, on a paper 'On the structure and affinities of fossil plants from the palæozoic rocks.— II. On spencerites, a new genus of lycopodiaceous cones from the coal measures, founded on the lepidodendron spenceri of Williamson' by Henry Dukinfield Scott to William Turner Thiselton-Dyer | 16 November 1897 |
| MC/23/415 | Letter from [Dukinfield Henry] Scott, East Oakley House, Oakley, Hants, to the [Royal Society] | 3 November 1908 |