Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/349

 In conclusion, we may inquire what light the reproductive organs figured by Goldenberg throw upon this question. These consist of several small sporangia borne on the dilated bases of slightly altered leaves. The sporangia in size and form agree exactly with what I have described in Flemingites ; but their arrangement on the supporting leaves is very different in the two genera. In Flemingites they are borne in a double row on the horizontal portion of the leaves which form the cone. I have recently detected similar sporangia associated with a true Lepidodendroid plant from a Carboniferous deposit from the South of Brazil. That these sporangia belonged also to the genus Sigillaria is very probable, independent of the direct observations of Goldenberg, from the enormous quantity of these capsules which occur in some coals, imparting to them special valuable properties.

Dr. Dawson says he has never found the detached fruits (Trigonocarpum and Rhabdocarpus) which he associates with Sigillaria attached to them ; and we need not, therefore, consider what claims they have to be so considered.

The structure of the fruits of Sigillaria and allied genera may be characterized as follows : —

Triplosporites, R. Br. Cone with a single sporangium borne on each scale ; the sporangia of the upper portion of the cone containing microspores, while those of the lower portion contain macrospores. Lepidostrobus, Brongn. Cone with a single sporangium on each scale ; all the sporangia filled with microspores.

Flemingites, Carr. Cone with a double series of small sporangia on each scale.

Sigillaria, Brongn. Cone with a single patch of small sporangia on the enlarged base of the scale.

It is probable, from the recent observations of Brongniart, that we as yet know the macrospores of only one genus, viz. Triplosporites, R. Br. ; but this would correspond with the state of our knowledge regarding the similar organs in the living Lycopodiaceoe ; for of the two principal genera of this Order, the microspores only are known in Lycopodium, while both kinds of spores occur in Selaginella.

EXPLANATION OF PLATE X.

Figs. 1-3. From a specimen of Stigmaria in which the whole of the cellular tissue had decayed and the spaces occupied by it had been filled with amorphous clay ; thereafter the vascular cylinder itself decayed, exposing the form of the medullary axis and the meshes for the vascular bundles. Fig. 1. Longitudinal section, showing that the meshes proceeded outwards at right angles to the axis. Fig. 2. The casts of the meshes, seen from above. Fig. 3. Ditto, seen from below.

Figs. 4-7. From a specimen of Stigmaria in which the vascular tissue is well preserved, but all the cellular structure has been replaced by amorphous material. Fig. 4. Transverse section of the vascular cylinder. Fig. 5. Oblique perpendicular section, gradually sloping outwards from above downwards. The vascular bundle is seen as a ridge at the base of the triangular cavity. This vascular ridge produces the double structure in the cast of the cellular cavity as seen from

T 2