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The below mentioned article provides short notes on Family Nilssoniaceae of Cycadales.
All reported members of this family of Cycadales are fossils. Its seed-bearing organs have been described as belonging to genus Beania while its leaves have been described under two fossil genera viz. Nilssonia and Pseudoctenis.The pollen-bearing organs of Nilssoniaceae are described as Androstrobus.
Beania, a fossil cycad, is represented by its seed-bearing structures. Its fossils have been reported from the Jurassic of Yorkshire. Harris (1961) described its two species viz. B gracilis and B mamayi. In both these species, the sporophylls were peltate and arranged spirally around the central cone axis.
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Two ovules were arranged on each sporophyll, and the entire cone was not a compact body but a loose structure (Fig. 8 55A). The sporophylls in B. gracilis (Fig. 8.55B) ranged from 1.5 to 2.5 cm in length and its entire cone attained a length of about 10 cm.
A hypothetical longitudinal section of its female sporangiophore (Fig. 8.55C) has been reconstructed by Harris (1961), and according to him in the lower two-third part of its seed the integument was fused to the nucellus but in the remaining one-third apical part the integument was free and not fused to the nucellus.
The integument was formed by an outer fleshy layer, middle stony layer and an inner fleshy layer. In the lower two-third part of the seed the vascular strands were seen running longitudinally in the integument. In B. mamayi, the sporangiophores were bifid structures.
Thomas and Harris (1960) described the male cones of Nilssoniaceae under the name Androstrobus. The pollen-bearing organs or male cones of A. manis (Fig. 8.55D) were compact bodies and had several spirally arranged peltate microsporophyll’s.
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Numerous finger-like pollen sacs were arranged irregularly on the abaxial side of each microsporophyll. In size these cones attained a length of about 5 cm and a breadth of about 2 cm.
The leaves attached to the plant, to which the male cones of Androstrobus manis were attached, have been described as Nilssonia compacta. These leaves were broadly linear and attained a length and breadth of about 40 cm and 9 cm, respectively.
The lamina of these leaves was cut irregularly into truncate segments. The veins were parallel and at right angle to the rachis of the leaf. Some scaly leaves were also seen attached to such plants.
In the Jurassic rocks the leaves of Nilssonia tenuinervis have been observed to be attached on the plant bearing male cones described as Androstrobus wonnacottii and female cones described as Beania mamayi. According the Harris (1961), the leaves described as Nilssonia tenuinervis were attached on such a plant which had a stout stem (Fig. 8.55A).
