Pteris, a common fern, grows extensively in cool, moist and shady localities.
The common Indian species of Pteris are P. longifolia, P. cretica, P. ensiformis, P. grandifolia, etc.
The Sporophyte of Pteris:
The rhizome may be either short and straight (as in P. longifolia, P. cretica, P. ensiformis, etc.), or long and creeping (as in P. grandifolia).
The internal anatomy of the rhizome is rather complicated and is very variable. Usually, in the cases of creeping rhizomes the vascular cylinder is a solenostele, but in the species with upright rhizomes it is a polycyclic dictyostele with prominent over lapping leaf gaps.
The roots are adventitious in nature and develop from the rhizome. Internally, the root represents essentially the structure of that of Polypodium.
The leaves are variable and range from pinnate compound to decompound type. Scales and un-branched hairs are generally present at the leaf bases as well as on the rhizomes forming ramenta. The leaves of the most commonly occurring species, P. longifolia, are imparipinnately compound and the pinnae are lanceolate in shape. The pinnae are sessile and situated laterally on both the sides of the rachis. Each pinna possesses a venation which is at first pinnate and then forked.
A cross-section of the rachis reveals the presence of a single horse-shoe shaped hadrocentric bundle with exarch xylem embedded in the ground tissue, as in Dryopteris.
The sporangia are grouped together forming continuous linear sori, termed as coenosori, borne on the marginal connecting veins. As a rule, these coenosori are not produced near about the apices of the pinnae and their continuity may be interrupted at irregular intervals. Each sorus is protected by the reflexed margin of the pinna itself, which forms a false indusium.
The structure of the sporangium as well as the process or fertilization are practically similar to those of Dryopteris.
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