. Fossil plants : for students of botany and geology . Paleobotany. 436 BBNNETTITALES [CH. Some reniform synangia (fig. 549, B) occur in the rock just above the cup. The sporophylls spread outwards from the base and then curve inwards, bending outwards again as they become free. A portion of a microsporophyll is shown in fig. 550 bearing segments projecting inwards as in W. sfectabilis (fig. 551). This specimen, which occurs in as- sociation with female flowers, is regarded by Mr Thomas as part of a unisexual flower. He discusses the possibihty of its connexion with an ovulate receptacle and e
. Fossil plants : for students of botany and geology . Paleobotany. 436 BBNNETTITALES [CH. Some reniform synangia (fig. 549, B) occur in the rock just above the cup. The sporophylls spread outwards from the base and then curve inwards, bending outwards again as they become free. A portion of a microsporophyll is shown in fig. 550 bearing segments projecting inwards as in W. sfectabilis (fig. 551). This specimen, which occurs in as- sociation with female flowers, is regarded by Mr Thomas as part of a unisexual flower. He discusses the possibihty of its connexion with an ovulate receptacle and expresses the opinion that if it were borne at the upper end of a bisporangiate flower the whole would be top-heavy and the arrangement uneconomical. On the other hand if, as suggested on page 434, the flowers were bisexual the staminate disc, which reached maturity before the ovules, may have been thrown off, as in Cycadeoidea, before the seeds were ripe. The form of the disc resembles that of the Indian specimen described on another page as Williamsonia sp., cf. W. setosa Nath.; it does not, I venture to think, afford an argument against the view that the microsporophyll-cup of some Williamsonia flowers was attached near the apex of the receptacle and was formed of modified foliar organs homologous with those which, in the ovulate portion of the flower, constitute the inter- seminal scales and megasporophylls. A further consideration of the microsporophylls of Williamsonia will be found in a later section of this chapter. Williamsonia spectabilis Nathorst. This species^, the first example of undoubted microspore- bearing organs referred to Williamsonia, was founded on material. Fig. 550. Williamsonia gigas. Side- view of an incomplete staminate disc showing the basal cup torn at the lower end and part of one of the free microsporophylls. (Diagrammatic drawing, after Thomas; nat. size.) 1 Nathorst (09) p. 6, Pis. jl., n; (11) p. 5, Pis. i., m; (12).. Please note that these imag
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