SOME CHROMOSOME COUNTS IN THE EUROPEAN CISTACEAE 159 



evolution seems to have proceeded largely by aneuploid variation early in the history 

 of the group. Polyploidy probably played a part in the origin of Tuheraria guttata, and 

 perhaps of Fumana. Bowden (1940) comments on finding a single tetraploid cell in 

 otherwise diploid H. canum, and I have found tetraploid cells in root tips of Tuheraria 

 vulgaris, Helianthemum chamaecistus and H. ledifolium. However a woody plant with a 

 limited life-span, and reproducing sexually from seed, may provide conditions hardly 

 more favourable than an annual for polyploid types to arise. Even so, it is surprising 

 that an annual should provide the only instance of polyploidy in a predominantly perennial 

 family. 



I gratefully acknowledge that the work on which this paper is based was carried out 

 during the tenure of a training grant given by the Nature Conservancy. I would like to 

 thank Dr. H. Godwin for his constant and stimulating interest in supervising my work, 

 and the following for their kindness in providing material : Dr. T. W. Bocher, Miss 

 M. E. Bradshaw, Dr. D. E. Coombe, Dr. A. R. Pinto da Silva, Dr. H. Godwin, Herr 

 A. Horn, Dr. W. Krause, Dr. C. D. Pigott, Dr. M. E. D. Poore, Prof. T. G. Tutin, 

 Dr. S. M. Walters. 



Summary : 



42 chromosome counts from 13 species of Cistaceae are listed and briefly discussed. 

 The distribution of the chromosome numbers in the family is as follows : 



2n 



Halimium 18 



Tuheraria sect. Eu-tuheraria 14 



sect. Scorpioides 36 



Helianthemum subgen. Helianthemum 20 



subgen. Plectolohum 22 



Fumana 32 



REFERENCES 



BOWDEN, W. M., 1940, Diploidy, polyploidy, and winter hardiness relationships in the flowering plants, 

 Am. BgL, 27, 357. 



CHIARUGI, A. N., 1925, Embriologia delle " Cistaceae," N. G. Bot. ltd., 33, 501. 



^ 1937, Contributo alia cariologia delle Cistaceae, N. G. Bot. Ital, 44, 641. 



DARLINGTON, C. D. & JANAKI AMMAL, E. K., 1945, Chromosome Atlas of Cultivated Plants, 

 London. 



GROSSER, W., 1903, Cistaceae, Pflanzenreich, IV 193. 



LOVE, a. & D., 1948, Chromosome numbers of northern plant species, Reykjavik. 

 MEUSEL, H., 1943, Vergleichende Arealkunde. Berlin. 



SNOAD, B., 1954, Abortive meiosis in plasmodial pollen mother cells of Helianthemum, Ann. Bot. N.S., 

 18, 1. 



TISCHLER, G., 1950, Die Chromosomenzahlen der Gefdsspflanzen Mitteleuropas. 's-Gravenhage. 

 TUTIN, T. G., 1953, Natural factors contributing to a change in our Flora, in Lousley, J. E. (cd.), The 



Changing Flora of Britain. London. 

 WARBURG, Sir O. E. & E. F., 1930, A preliminary study of the genus Cistus, /. R. Hort. Soc, 55, 1. 



