> [!cite] BHL link: this entry starts at [page 190](https://www.biodiversitylibrary.org/page/33265867) of TL-2 Suppl. IV > Author links: [IPNI](https://www.ipni.org/a/1675-1) LSID 1675-1, [Wikidata](https://www.wikidata.org/wiki/Q1687144) QID Q1687144 > Support pages: [[Abbreviations|abbreviations]], [[Layout key|layout key]], [[Cite TL-2|cite TL-2]] ### Author Clausen, Jens \[Christian\] (1891-1969), Danish botanist and geneticist, born near Tølløse (Seeland), educated at the secondary school at Tølløse, studied at the University of Copenhagen, with the staff of the Dept. Genetics Royal Veterinary and Agricultural High School, Copenhagen 1921-1931 with Ø. Winge, Dr. phil. ib. 1926, head of the division of plant biology of the Carnegie Institution of Washington in Stanford, Calif. 1931 (from 1932 for experimental taxonomy), professor of biology at Stanford University 1951-1969. **Abbreviated name**: *J.C. Clausen* \[standard form in IPNI: *J.C.Clausen*\] #### Herbarium and types [[Collection CAS|CAS]] (originally at [[Collection CI|CI]] and [[Collection DS|DS]], including the Clausen, Keck and Hiesey material), also [[Collection C|C]] (2000), [[Collection US|US]]. #### Bibliography and biography Barnhart 1: 354 (b. 11 Mar 1891, Holback, Amt., Denmark); Christiansen p. 313 \[index\]; Hortus 3: 1190; IH 1(ed. 8): 451(CI), 2: 129; Kew 1: 565-566; NAF ser. 2. 5: 234; TL-2/suppl.: 19.768. #### Biofile - Anon., Amer. men sci. ed. 5: 205. 1933; Bot. Not. 110: 290. 1957; Madroño 18: 174-175. 1966. - Böcher, T.W., Taxon 19(3): 351-352. 29 Jun 1970 (obit., text used for our caption). - Christensen, C., Danske bot. Litt. 1912-1939: 210-211. 1940 (nos. 1-30). - Ewan, J. et al., Short hist. bot. U.S. 163. 1969. - Fox Maule, A., Bot. Tidsskr. 69: 199. 1974. - Hagen, J.B., Taxon 32(3): 410. 1983. - Hansen, A., Dansk bot. Ark. 21(1): 57. 1963. - Hunt Institution, Biogr. dict. bot. portr. coll. 77. 1972. - Thomas, J.H., Huntia 3: 31. 1969. - Vickery, R.K., Genetics 68(1): 96-97. 1971 (obit.). ### Publications ##### n.26.502. Studies of the collective species Viola tricolor **Title** *Studies of the collective species Viola tricolor* L. (Preliminary notes)... Saertryk af Botanisk Tidsskrift... 1921 \[-1922\]. Oct. **Notes** *Publ*.: \[*1*\]: 1 Sep 1921 (in journal), p. \[205\]-221, *pl. 1-3* (uncol.). *Copy*: L. – Reprinted and to be cited from Bot. Tidsskr. 37(3): 205-221, *pl. 1-3.* 1921. *2*: 1 Dec 1922 (in journal), cover-t.p., p. \[363\]-416. *Copies*: B, L. – Id. 37(5): 363-416. 1922. – See also W. and W. Christiansen, Bot. Schriftt. Schlesw.-Holst., Kiel 98. 1936. *Note*: See also his *Stedmodersblomsters* \[Viola\] *variation*, Nat. Verden 7: 218-236. 1923. ##### n.26.503. Increase of chromosome numbers in Viola **Title** *Increase of chromosome numbers in Viola* experimentally induced by crossing... Separat ur Hereditas... 1924. Oct. **Notes** *Publ*.: 1924 (p. 32: date of mss. 5 Jan 1924), cover-t.p., p. \[29\]-32. *Copy*: L. – Reprinted and to be cited from Hereditas 5: 29-32. 1924. ##### n.26.504. Genetical and cytological investigations on Viola tricolor **Title** *Genetical and cytological investigations on Viola tricolor* L. and V. arvensis Murr. ... Lund, Hereditas... 1926. Oct. **Notes** *Publ*.: 1926, p. \[1\]-156, *2 pl*. (col.). *Copy*: n.v., see C. Christensen 1940, no. 26. – Reprinted from Hereditas 8: 1-156, *2 pl*. 1926. *Ref*.: Wilmott, A.J., J. Bot. 65: 59. Feb 1927 (rev.). ##### n.26.505. Non-Mendelian inheritance in Viola **Title** *Non-Mendelian inheritance in Viola*... Separat ur Hereditas... 1927. Oct. **Notes** *Publ*.: 3 Feb 1927 (date on cover-t.p.: "Festschrift för W. Johannsen 3 Feb 1927"), cover-t.p., p. \[245\]-256. *Copy*: L. – Reprinted and to be cited from Hereditas 9: 245-256. 1927. ##### n.26.506. Synspunkter vedrørende Evolutionslaeren **Title** Nogle nyere *Synspunkter vedrørende Evolutionslaeren*... \[Saertryk af Naturens Verden... 1927\]. Oct. **Notes** *Publ*.: Mai 1927 (date on cover, first part \[p. 145-161\] Apr 1927), cover (identif.), p. \[145\]-161, 193-214. *Copy*: L. – Reprinted and to be cited from Nat. Verden 11: 145-161, 193-214. 1927. ##### n.26.507. Chromosome number **Title** *Chromosome number* and the relationship of species in the genus *Viola*... Annals of Botany 1927 \[-1929\]. Oct. **Notes** *Publ*.: \[*1*\]: Oct 1927 (date on cover-t.p.), cover-t.p., p. \[677\]-714. *Copy*: L. – Reprinted and to be cited from Ann. Bot. 41(164): 677-714. 1927. \[*2*\]: Oct 1929 (date on cover-t.p.), cover-t.p., p. \[741\]-764. *Copy*: L. – Id. 43(172): 741-764. 1929. ##### n.26.508. Exchange between chromatids of homologous chromosomes **Title** *Exchange between chromatids of homologous chromosomes*... Det 18. Skandinaviske Naturforskermøde 1929. Oct. **Notes** *Publ*.: 1929 (text read at congress in Copenhagen 26-31 Aug 1929), p. \[1-7\]. *Copies*: B, L. – Reprinted and to be cited from Report 18. Skand. Naturalist Congress in Copenhagen 26-31 Aug 1929, p. 239-245. 1929. ##### n.26.509. Danmarks Viol-Arter **Title** *Danmarks Viol-Arter* (The Viola-species of Denmark)... Saertryk af Botanisk Tidsskrift... 1931. Oct. **Notes** *Publ*.: 1 Jul 1931 (in journal), cover-t.p., p. \[317\]-335. *Copy*: L. – Reprinted and to be cited from Bot. Tidsskr. 41(4): 317-335. 1931. ##### n.26.510. Genetic studies in Polemonium **Title** *Genetic studies in Polemonium*. III. Preliminary account on the cytology of species and specific hybrids... Separat ur Hereditas... 1931. Oct. **Notes** *Publ*.: 1931, p. \[62\]-66. *Copies*: B, FAS(B), L. – Reprinted and to be cited from Hereditas 15: 62-66. 1931. *Notes*: (1): *Genetic studies in Polemonium coeruleum* by C.E.H. Ostenfeld (1873-1931), see TL-2/3: 854-856 (a preliminary report), *in* Hereditas 4(1923). - (2): *Genetic studies in Polemonium*. II, Experimental crosses... by id. ##### n.26.511. Viola canina **Title** *Viola canina* L. a cytologically irregular species... Separat ur Hereditas... 1931. Oct. **Notes** *Publ*.: 1931, cover-t.p., p. \[67\]-88. *Copy*: L. – Reprinted and to be cited from Hereditas 15: 67-68. 1931. ##### n.26.512. Cyto-genetic and taxonomic investigations on Melanium Violets **Title** *Cyto-genetic and taxonomic investigations on Melanium Violets*... Separat ur Hereditas... 1931. Oct. **Notes** *Publ*.: 1931 (before 1 Oct 1931 on which date Clausen would be at Stanford University, Palo Alto, Calif. according to a note on the cover-t.p.), cover-t.p., p. \[219\]-308. *Copy*: L. – Reprinted and to be cited from Hereditas 15: 219-308. 1931. ##### n.26.513. Bruun's paper **Title** Remarks upon H.G. *Bruun's paper* on *Viola canina* L.... Separat ur Hereditas... 1932. Oct. **Notes** *Publ*.: 1932, p. \[67\]-70. *Copy*: L. – Reprinted and to be cited from Hereditas 17: 67-70. 1932. *Note*: Helge Gösta Bruun (1877-x), see TL-2, suppl. 3: 168. ##### n.26.514. Experimental taxonomy **Title** *Experimental taxonomy*... Reprinted from... Carnegie Institution... 1933\[-1944\]. Oct. **Notes** *Co-authors*: David Daniels Keck (1903-x), see TL-2/2: 512 and William McKinley Heusi \[later: Hiesey\] (1903-x), see TL-2/2: 194. *Publ*.: 15 Dec 1933 (date on p. \[1\]), p. \[1-4\]. *Copies*: FAS(B), L. – Reprinted and to be cited from Ann. Rep. Div. Pl. Biol., Carnegie Inst. Year Book 32: 192-196. 1933. *Note*: Jens Clausen, D.D. Keck and W.M. Hiesey published numerous articles with the title *Experimental taxonomy*. They are not numbered. We list here the publications seen by us. *1934*: 14 Dec 1934, p. \[173-177\]. *Copy*: L. – Reprinted from id. 33: 173-177. 1934. *1935*: 13 Dec 1935, p. \[201\]-206. *Copies*: B, MO. – Id. 34: 201-206. 1935. *1936*: 11 Dec 1936, p. \[208\]-214. *Copies*: B, G, MO. – Id. 35: 208-214. 1936. *1937*: 10 Dec 1937, p. 209-214. *Copies*: G, L. – Id. 36: 209-214. 1937. *1938*: 9 Dec 1938, p. \[218\]-222. *Copies*: G(2), L. – Id. 37: 218-222. 1938. *1939*: 15 Dec 1939, p. 123-127. *Copies*: B, G, L. – Id. 38: 123-127. 1939. *1940*: 13 Dec 1940, p. \[i\], 158-163. *Copies*: G, L, MO. – Id. 39: 158-163. 1940. *1941*: 12 Dec 1941, p. \[i\], 160-170. *Copies*: G, L. – Id. 40: 160-170. 1941. *1942*: 18 Dec 1942, p. \[i, recto of 126\], 126-134. *Copy*: L. – Id. 41: 126-134. 1942. *1943*: 7 Dec 1943, p. 91-100. *Copy*: L. – Id. 42: 91-100. 1943. *1944*: 15 Dec 1944, p. 69-81. *Copy*: L. – Id. 43: 69-81. 1944. ##### n.26.515. basis for natural systematic units **Title** The *basis for natural systematic units*... Nordiska (19. Skandinaviska) naturforskarmötet i Helsingfors 1936. Oct. **Notes** *Publ*.: 1936, p. \[1\]-4. *Copies*: FAS(B), L. – Reprinted and to be cited from Nordiska (19. Skandinaviska) naturforskarmötet i Helsingfors 1936, p. 520-523, discussion on p. 523-524 not included in reprint. ##### n.26.516. The concept of species based on experiment **Title** *The concept of species based on experiment*... Reprinted from The American Journal of Botany... 1939. Oct. **Notes** *Co-authors*: David Daniels Keck (1903-x), see TL-2/2: 512 and William McKinley Hiesey (1903-x), see TL-2/2: 194. *Publ*.: Feb 1939 (date on p. \[103\]), p. \[103\]-106. *Copies*: B, FAS(B), L. – Reprinted and to be cited from Amer. J. Bot. 26(2): 103-106. 1939. ##### n.26.517. Experimental studies on the nature of species **Title** *Experimental studies on the nature of species*. I. Effect of varied environment on Western North American plants... Washington, D.C. (Carnegie Institution of Washington Publication...) 1940 \[-1948\]. Oct. **Abbreviated title**: *Exper. stud. species*. **Notes** *Co-authors*: David Daniels Keck (1903-x), see TL-2/2: 512 and William McKinley Hiesey (1903-x), see TL-2/2: 194. *Publ*.: 12 Jul 1940 (date on p. ii), p. \[i\]-vii, \[viii\], \[1\]-452. *Copies*: FAS(B), MO. *2*. *Plant evolution through amphiploidy* and autoploidy,... Washington D.C. 1945. Oct. (*Pl. evol. amphipl.*), p. \[i\]-vii, \[1\]-174. *Copies*: FAS(B), MO. *3*. *Environmental responses* of climatic races of Achillea 1948. Oct. (*Environm. resp.*), p. \[i\], \[1\]-129. *Copies*: FAS(B), MO. *Ref*.: Mason, H.L., Madroño 6(2): 60-63. 15 Apr 1941 (rev.). ##### n.26.518. Regional differentiation in plant species **Title** *Regional differentiation in plant species*... Reprinted from The American Naturalist ... 1941. Oct. **Notes** *Co-authors*: David Daniels Keck (1903-x), see TL-2/2: 512 and William McKinley Hiesey (1903-x), see TL-2/2: 194. *Publ*.: Mai-Jun 1941 (in journal), p. 231-250. *Copy*: L. – Reprinted and to be cited from Amer. Natural. 75(758): 231-250. 1941. ##### n.26.519. Relations between climate and intraspecific variation in plants **Title** *Relations between climate and intraspecific variation in plants*... Reprinted from The American Naturalist... 1942. Oct. **Notes** *Co-authors*: David Daniels Keck (1903-x), see TL-2/2: 512 and William McKinley Hiesey (1903-x), see TL-2/2: 194. *Publ*.: Jan-Feb 1942, p. 5-22. *Copy*: L. – Reprinted and to be cited from Amer. Natural. 76(762): 5-22. 1942.