| Betulaceae | |
| Publ. & Syn. | C. DC. in DC., Prodr. 16, 2: 148 (1864). Described from Kamtchatka and the Amur area (the Russian Far East) and from Sitka (Alaska). - Myrica tomentosa (C. DC.) Asch. & Graebn., Syn. Mitteleur. Fl. 4: 353 (1910). - Myrica gale subsp. tomentosa (C. DC.) E. Murray, Kalmia 12: 22 (1982). |
| Notes | The base chromosome number in the two genera, Alnus and Betula, is usually assumed to be x = 14 and the species with 2n = 28 and 56 to be, respectivelly, diploids and tetraploids. There are, however, a few species consistently counted with intermediate numbers (e.g., Betula divaricata with 2n = 42 = 3x; B. kenaica and B. papyrifera with 2n = 70 = 5x), suggesting that the base number may be 2n = 7. This could explain the high seed fertility found in assumedly triploid (i.e., hexaploid) hybrids (2n = 42), e.g., between B. nana (2n = 28) and B. pubescens (2n = 56). For simplicity, the traditional levels are included below. |
| Chromosomes | (1) 48 (6x). - Far East (Sakhalin). - Sokolovskaya (1960a). (2) 96 (12x). - Canada (British Columbia). - At least three reports. |
| Geography | Amphi-Pacific: ALA. |
| Child taxa |
Alnus Mill. Betula L. |
| PAF ID | 61 |