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| Keywords: The Quarterly journal of the Geological Society of London (12893458343).jpg 32 <br> MR A C SEWARD ON CYCADEOIDEA GIGANTEA Feb 1-897 <br> shoot must unfortunately remain a <br> veloped fronds or a floral <br> matter for speculation 1 <br> It remains for us to consider more fully the affinities of the <br> Portland fossil stem Externally it would be difficult to discover <br> any real difference between the fossil and many large trunks of <br> recent Cycads especially some species of Macrozamia and Enceplial- <br> artos In recent stems the <br> older petiole-bases may be Pig 4 ” The apical bud of Encephal- – <br> frequently seen to have artos Altensteinii <br> rotted away internally <br> while a peripheral band of <br> more resistant material <br> periderm or sclerenchyma <br> has remained as a project- <br> ing ridge 2 In the fossil <br> stem it is more particularly <br> the interpetiolar tissues <br> that have remained as the <br> prominent surface-feature <br> Passing to the internal <br> structure there is a close <br> correspondence between the <br> fossil petioles and those of <br> living Cycads In a trans- <br> verse section of a recent <br> petiole taken some inches <br> above the base there is a <br> well-developed hypodermal <br> mass of sclerenchyma in- <br> terspersed with groups of thin-walled parenchyma If a series of <br> sections be cut from a petiole until the base is reached the scleren- <br> chymatous hypoderm is found to gradually decrease in amount and <br> is finally almost or entirely absent A cork-cambium arises in the <br> persistent basal portion either in the subepidermal layer orina deeper <br> layer of cells and a ring of periderm is developed This increase <br> in the diameter of the old leaf-bases of Cycads has been alluded to <br> by Saporta 3 Eenault 4 Solms-Laubach 5 and others In the fossil <br> stems we have an exactly similar formation of periderm in the <br> petiole-bases The leaf-bases of Dioon eclule as well as those of <br> the species of Macrozamia M Denisoni figured in PL III fig 2 <br> illustrate very clearly the disappearance of the sclerenchyma and the <br> formation of cork In Dioon edule the phellogen occurs internal <br> 1 Lester Ward has pointed out U S Geol Surv 16th Ann Rep 1896 <br> p 487 that one of the specimens of Bennettites Cycadeoidea Saxbyana in the <br> British Museum possesses an apical leaf -bud This however is very much less <br> distinct than the bud in the Portland stem <br> 2 This is particularly well shown in a piece of a stem of Macrozamia <br> Moorei in the Museum Few Gardens <br> 3 Pal Frang vol ii 1875 Cycadees p 11 <br> 4 ' Cours de Bot foss ' vol i 1885 p 35 <br> 5 ' Die Sprossfolge der Stangeria u der iibrigen Cycadeen 'Bot Zeit Jahrg <br> xlviii p 12 See also Eichler in Engler Prantl op jam cit p 7 <br> From a photograph of a plant in the Palm <br> House Royal G-ardens Kew 36028737 111130 51125 Page 32 Text 53 http //www biodiversitylibrary org/page/36028737 1897 Geological Society of London NameFound Bennettites Cycadeoidea NameConfirmed Bennettites W Carruthers 1870 NameBankID 4927367 NameFound Cycadeoidea gigantea NameFound Dioon NameConfirmed Dioon EOLID 20727 NameBankID 606462 NameFound Dioon edule NameConfirmed Dioon edule EOLID 2496645 NameBankID 606463 NameFound Macrozamia NameConfirmed Macrozamia EOLID 30050 NameBankID 2663711 NameFound Stangeria NameConfirmed Stangeria EOLID 30057 NameBankID 2663707 Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 53 1897 Geology Periodicals Smithsonian Libraries bhl page 36028737 dc identifier http //biodiversitylibrary org/page/36028737 smithsonian libraries Information field Flickr posted date ISOdate 2014-03-03 Check categories 2015 August 26 CC-BY-2 0 BioDivLibrary https //flickr com/photos/61021753 N02/12893458343 2015-08-26 17 56 28 cc-by-2 0 PD-old-70-1923 The Quarterly journal of the Geological Society of London 1897 Photos uploaded from Flickr by Fæ using a script | ||||
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