Historic fossil cycads ; Accelerated cone growth in Pinus / by G.R. Wieland.

  • George Reber Wieland
Date:
1908
Catalogue details

Licence: In copyright

Credit: Historic fossil cycads ; Accelerated cone growth in Pinus / by G.R. Wieland. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    fication period well illustrated by Cycadeoidea megalophylla Bucldand ; and, as indicated by large groups of bracts marking the individual axes of fructification, and especially by the man- ner in which the bracts close in compactly at the center of the bract groups, many young fruits are present. Of these fruits three, and perhaps more, are very clearly in the bisporangiate or nondehiscent-disk or flower-bud stage so well exhibited by our American specimens. Moreover, in one of these three buds the disk structure is strikingly clear. In it the curved middle portions of the unexpanded and presumably bipinnate microsporophylls have been so eroded away as to clearly reveal in transverse section sixteen circularly disposed micro- sporophyll rachides. And one may plainly see that these sec- tions of the rachides of triangular outline abut and enclose an inner mass of closely packed and wonderfully conserved synangia of large size, rising above and concealing a central ovulate cone. The individual synangia are evidently attached to the rachides in normal position. This is the first time that the presence of such silicified flowers has been definitely confirmed in European trunks.* In size and general structure the bisporangiate strobilus of C. Reichenbachiana with its 16 microsporophylls closely agrees with that of C. dacotensis with 17 or 18, with perhaps a decid- edly interesting difference in the apparently larger size of the synangia. The structure of the synangia is unquestionably preserved ; indeed, although familiar with quite 1,000 trunks, I know of no other fossil cycad so beautifully and magnificently silicified as C. Reichenbachiana. It is even probable that the entire structure of the staminate fronds as well as the synangia is preserved in the greatest perfection, whence it is>of very distinct interest to paleobotanists that, as 1 was informed at Dresden, Solms-Laubach is soon to carry out an exhaustive histologic study of this famous fossil cycad. * I am unable to reconcile the features of C. Reichenbachiana with the drawing of the “ Bruchstuck” given by Goeppert on Plate IX of the Jubi- lauius Denkschrift, published in 18o3. In fact not only this, but all the accompanying figures are of that uncertain value so characteristic of most illustrations of fossils previous to the extended use of photography,—and that they are quite inexact has already been observed by Professor Ward. With the Dresden cycad before me it seemed that the large Williamsonia- like fruit nearly 5 centimeters in diameter and so prominent in Goeppert’s Plate IX must pertain to an accompanying fragment, or even to another specimen ; but as the text of the Denkschrift gives no clue to any such, I must conclude that during or since the time of Goeppert the fruit illus- trated was partly or wholly broken away. Goeppert supposed these axes to be vegetative and like the lateral buds of old Cycas stems: but Professor Ward notes that they are fruits and thought seeds must be found in some. In which he is wholly correct, since nearly all must bear young ovulate cones hidden beneath the thick husk of enclos- ing bracts, which is in the great majority of cases all that can be seen at the surface of the trunk. Fully fifty young floral axes are present.
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