| As in the ferns, the heterosporous representatives have much lower chromosome numbers than do the homosporous groups. |
| A heterosporous life history occurs in some pteridophytes and in all seed plants. |
| This uncommon situation is called functional heterospory and may represent the means by which the heterosporous condition in vascular plants evolved from the homosporous condition. |
| Isoetes is heterosporous, with each leaf a potential microsporophyll or megasporophyll. |
| Their heterosporous life cycle is likely to be an adaptation to their aquatic habit. |
| Many paleobotanists believe that the earliest seed plants evolved from heterosporous Middle Devonian plants like the progymnosperms. |
