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How do the primitive and advanced species of Equisetum differ in their shoots?
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Equisetopsida
Giant horsetail of Europe (Equisetum telmateia).
In the genus Equisetum, the primary distinction between primitive and advanced species lies in the nature and specialization of their shoots:
- Primitive species: These are characterized by perennial, green shoots that perform both vegetative and reproductive functions.1
- Advanced species: These exhibit a division of labor, typically producing annual, green, branched vegetative shoots alongside separate, often nongreen, unbranched fertile shoots.1
Some species may display intermediate combinations of these features. In those that produce separate shoots, the fertile (strobilate) branches typically emerge first to shed spores, followed by the development of the green vegetative shoots.1