[ 780177] 
VIII. On the Structure and Affinities of Stephanospermum, Brongniart, a Genus of 
Fossil Gymnosperm Seeds. By F. W. Ourver, M.A., D.Sc., F.L.S., Quain Professor 
of Botany, University College, London. 
(Plates 41-44.) 
Read 5th February, 1903. 
Contents, 
A Page Pago 
ceux m AP e E uge en vie os ov evel 361 The Structure of the Pollen. 
Stephanospermum akenioides. Pollen of Stephanospermum akenioides .... 376 
MEUM Dirueture a.i =e ono rin oni . 363 Pollen of Stephanospermum caryoides  .... 379 
EN And Chalasa .,....... 0623 eens . 364 The Question of Pollen-tubes............ 383 
Nucellus and Pollen-chamber........... . 368 The Difference of Pollen-strueture ...... 335 
Nusella? Beak. A". EE « EE Characters distinguishing Steph. caryoides...... 338 
Stephanospermum caryoides. Fertilisation and the Tracheal Mantle ........ 356 
General Remarks... dë Aale Kerg" SCH Comparison with other Paleozoic Seeds ...... 389 
FORE |b EE E 374 Summary and Conclusion `... ek ENN KE 304 
INWOCHUS ` 5842 102 25112 0087 DEUS 914 Explanation of the Platea... € ter ee tn 296 
INTRODUCTION. 
THE last of many notable contributions to Fossil Botany by Adolphe Brongniart was 
a general account of the morphology of a large series of silicified seeds from the pebbles 
of Grand’ Croix, near St. Etienne. Originally published in 1874*, this contribution 
was re-issued in 1881 with numerous beautiful plates some years after his death as a 
memorial volume f. Of seeds having what may be termed a Cycadean organisation, 
Brongniart enumerates seventeen genera, a number which has been increased since. In 
the years that have elapsed since Brongniart's time many of these forms have been 
elaborated in greater detail by his followers, especially Renault, and in rare instances it 
has been possible to produce adequate evidence for referring a certain number to the 
plants to which they belonged. To this day the great bulk of the French seeds found 
in the later Palzeozoic rocks, as also the less numerous forms from the English Coal- 
Measures, are known as detached structures, and their real affinity is a matter of 
conjecture. Notwithstanding this limitation, that we know these seeds only as detached 
structures, so important a portion of the plant is the seed that a detailed knowledge of 
the organisation of fossil seeds cannot fail to be a useful adjunct in unravelling the 
intricate phylogenetic history of recent plants. 
It was in connection with one of these fossils—Stephanospermum—that Brongniart 
* Ann. Sc. Nat., Bot. 5* sér. t. xx. (1874) pp. 234-265, pls. 21-23. 
T ‘Recherches sur les Graines fossiles silicifiées, 1831. 
SECOND SERIES.—BOTANY, VOL. VI. : Se 
