AP BIOLOGY

Detailed explanation-1: -feature of Equisetopsida …of the strobilus are called sporangiophores; each consists of a stalk bearing a flattened disk at its apex, on the lower edge of which is a ring of 5 to 10 sporangia, each one opening and shedding spores by a longitudinal slit on its inner side. The Carboniferous treelike horsetails…

Detailed explanation-2: -Each sporangiophore is a stalked structure bearing a hexagonal peltate disc at its distal end (Fig. 7.86D). On the under surface of the sporangiophore disc 5-10 elongate, cylindrical hanging sporangia are borne near the periphery in a ring.

Detailed explanation-3: -The spores are borne under sporangiophores in strobili, cone-like structures at the tips of some of the stems. In many species the cone-bearing shoots are unbranched, and in some (e.g. E. arvense, field horsetail) they are non-photosynthetic, produced early in spring.

Detailed explanation-4: -Inner cortex is made up of large parenchymatous cells with vallecular canals. Stele: Eustele, siphonostele; ring of vascular bundles below the ridges. Xylem is poorly developed.