The Female Reproductive Organs of Conifers and Taxads

Abstract

SUMMARY The morphology of the female conifer cones has long been a matter of dispute. In 1900 an account of the theories put forward so far was given by Worsdell. After a brief characterization of the situation at that time, the present article deals with the later history of the subject. At the turn of the century there were rivalling concepts of the nature of the so‐called ovuliferous scale in the conifers: (a) the Excrescence or Ligular theory of Sachs‐Eichler, (b) the general Brachyblast theory of Braun, Caspary, čelakovský and others, (c) van Tieghem's modification of the Brachyblast theory, and (d) the Foliolar theory of Delpino‐Penzig. In the subsequent three decades the discussion proceeded on the same or similar lines. The Excrescence theory retained a strong position until the end of the nineteen‐twenties, but, as before, some morphologists professed the general Brachyblast theory. Herzfeld and Wettstein considered that the axillary conifer strobilus had one or more reduced carpels (megasporophylls) which were used up in the formation of terminal ovules, as well as an ‘ovuliferous scale’ consisting of secondary outgrowths from the strobilar axis. In Goebeľs opinion these outgrowths were instead produced by the megasporophylls. Doubts were expressed of the unity of the true conifer group, but Eames showed that the apparently widely different female cones of the Pinaceae and Araucariaceae are homologous, and that the Araucariaceae, Taxodiaceae and Podocarpaceae exhibit complete transitions by fusion and reduction from types with distinctly compound strobilar units–each with an ‘ovuliferous scale’ in the axil of a bract–to others of the most simple form. In contradistinction to the true conifers, the genus Taxus has no compound strobilus, and its ovule is a direct continuation of the axis of the fertile short shoot (Dupler). In the first half of the period after 1930 opinions differed as much as ever, although the general Brachyblast theory now prevailed over the Excrescence theory and other concepts. Chadefaud believed the ‘ovuliferous scale’ and the bract to represent between them a carpel derived from a prototype analogous to the pinnate megasporophyll of Cycas. Hirmer interpreted the ‘ovuliferous scale’ and the bract as formed by a serial splitting of one single member. Lanfer supported Goebeľs views of the terminal position of the conifer ovules on reduced megasporophylls, and of the nature of the ‘ovuliferous scale’. In Hagerup's opinion the female cones of most true conifers are compound and have a short secondary axis developed axillary to each bract. This axis was supposed to carry two transversal prophylls, fertile (megasporangial) or sterile, and a varying number of sterile leaves; and the megasporophyll, with a megasporangium on its upper side, to constitute the integument of the ovule, and be homologous to a lycopod sporophyll. Florin (1938‐45) found that the Palaeozoic cordaites and conifers furnished the principal clue to the interpretation of the true conifer cones of Mesozoic and more re...

Phylogeny of Taxaceae and Cephalotaxaceae Genera Inferred from Chloroplast matK Gene and Nuclear rDNA ITS Region

“…It should be stressed that nr18S rRNA sequences are too conserved to resolve relationships among these two close families and that Stefanovic et al used a relatively short length of the nr28S sequences (683 bp). The phylogenetic analyses presented here confirm the inferences of the morphological studies of Hart (1987) and Price (1990) but refute the claims of Florin (1948Florin ( , 1954 and Singh (1961) that Cephalotaxaceae has no alliance with Taxaceae.…”

“…The fossil record of Cephalotaxus is very limited, and its ancestry is still unclear (Miller, 1977). Florin (1948Florin ( , 1954 considered the Cephalotaxceae as having no alliance with Taxaceae. This opinion was further defended by Singh (1961), who claimed that similarities between the two families, such as spiral thickening in the xylem tracheids, unwinged pollen grains without prothallial cells, and embryogeny, were also found in other conifer families.…”

Aspects of Permian palaeobotany and palynology. IV. The conifer Ortiseia florin from the val gardena formation of the dolomites and the Vicentinian alps (Italy) with special reference to a revised concept of the Walchiaceae (Göppert) Schimper

“…However, especially as a result of the work by Florin (1938Florin ( --1945, it became generally accepted that ovuliferous cones are compound, the "seed-scales" representing transformed shoots of limited growth (ovuliferous dwarf-shoots) in the axils of bracts. For a survey of the various theories about the organization of ovuliferous cones, one is referred to the work of Pilger (1926), Florin (1954), Lam (1954) and Grauvogel-Stamm (1978).…”

Cone Crops of White and Black Spruce Are Predictable

“…investigators consider the ovuliferous scale a fused structure consisting of one or two leaves on a greatly reduced modified shoot (Aase 1915, Doak 1935, others consider it to be a modi6ed flattened short shoot without foliar components (Florin 1954). The male strobilus bears only primary components and the microsporophyll is a simple foliar structure, though it bears two pollen sacs.…”